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Ndzukuma, Sibusiso. "Statistical tools for wind energy generation." Thesis, Nelson Mandela Metropolitan University, 2012. http://hdl.handle.net/10948/d1020627.
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In this study we conduct wind resource assessment to evaluate the annual energy production of a wind turbine. To estimate energy production of a wind turbine over a period of time, the power characteristics of the wind turbine are integrated with the probabilities of the wind speed expected at a chosen site. The first data set was obtained from a wind farm in Denmark. We propose several probability density functions to model the distribution of the wind speed. We use techniques from nonlinear regression analysis to model the power curve of a wind turbine. The best fit distribution model is assessed by performing numeric goodness–of–fit measures and graphical analyses. Johnson’s bounded (SB) distribution provides the best fit model with the smallest Kolmogorov–Smirnov (K-S) test statistic . 15. The four parameter logistic nonlinear regression (4PL) model is determined to provide the best fit to the power curve data, according to the Akaike Information Criterion (AIC) and the Bayesian Information Criterion (BIC). The estimated annual energy yield is compared to the actual production of the wind turbine. Our models underestimate the actual energy production by a 1 difference. In Chapter Six we conduct data processing, analyses and comparison of wind speed distributions using a data set obtained from a measuring wind mast mounted in Humansdorp, Eastern Cape. The expected annual energy production is estimated by using the certified power curve as provided by the manufacturer of the wind turbine under study. The commonly used Weibull distribution is determined to provide the best fit distribution model to our selected models. The annual energy yield is estimated at 7.33 GWh, with a capacity factor of 41.8 percent.
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Bezerra, Rufino Ferreira Paiva Eduardo. "Wind Velocity Estimation for Wind Farms." Electronic Thesis or Diss., Université Paris sciences et lettres, 2023. http://www.theses.fr/2023UPSLM046.
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Cette thèse propose des algorithmes pour estimer la vitesse et la direction du vent pour des éoliennes et des parcs éoliens.Tout d'abord, nous proposons des méthodes basées sur les données pour estimer la vitesse effective du rotor (REWS) sans nécessiter la connaissance de certains paramètres physiques de l'éolienne, qui pourraient être inconnus de l'opérateur. Nous fournissons deux méthodes basées sur les données, l'une basée sur la régression par processus gaussien et l'autre combinant la régression par processus gaussien avec un observateur grand gain.Ensuite, en nous basant sur cette estimation locale de la REWS, au niveau d'une éolinenne, nous abordons la question de l'estimation du vent en écoulement libre au niveau du parc éolien.Nous commençons par nous concentrer sur l'estimation de la vitesse du vent, pour une direction du vent connue. Pour un parc éolien de géométrie simple, nous démontrons qu'une mesure locale de la vitesse perturbée par la présence des éoliennes peut être utilisée pour estimer la vitesse du vent en écoulement libre. Nous fondons notre méthodologie d'estimation sur une modélisation simplifiée de l'effet de sillage qui consiste en des équations aux dérivées partielles hyperboliques du premier ordre en cascade, et dont la vitesse de transport est la vitesse du vent en écoulement libre. Nous proposons d'utiliser une solution analytique de ces équations, impliquant des retards de transport, pour effectuer une estimation de la mesure locale et mettre à jour l'estimation de la vitesse du vent en écoulement libre. Nous démontrons formellement la convergence de cette estimation et illustrons numériquement l'efficacité de cette méthode.Enfin, nous passons à une configuration plus générale où à la fois la vitesse et la direction du vent en écoulement libre sont inconnues. Nous proposons d'utiliser une modélisation bidimensionelle du sillage et de nous appuyer sur une méthode basée sur l'optimisation. Le problème d'identification que nous formulons se révèle être particulièrement difficile en raison de l'apparition de retards de transport, mais nous montrons comment contourner cette difficulté en considérant une valeur moyenne de l'historique de la vitesse du vent en écoulement libre. Des résultats de simulation obtenus avec le simulateur FAST.Farm illustrent l'intérêt de la méthode proposéeThis thesis designs algorithms to estimate the wind speed and direction for wind turbines and wind farms.First, we propose data-based methods to estimate the Rotor Effective Wind Speed (REWS) for a single turbine without prior knowledge of certain physical parameters of the turbine that might be unknown to an operator.We provide two data-based methods, based respectively on Gaussian Process Regression (GPR) and on an combination of GPR with high-gain observers.Second, grounding on this REWS estimation at the local level of one turbine, we address the question of estimating the free-flow wind at the level of a wind farm.We start by focusing on wind speed estimation, for a given known wind direction. For a wind farm with a simple geometry, we prove that a local speed measurement disturbed by the presence of the turbines can be used to estimate the free-flow wind speed. We ground our estimation methodology on a simplified wake model, which consists of first-order hyperbolic partial differential equations, the transport speed of which is the free-flow wind speed. We propose to use an analytical solution of these equations, involving transport delays, to perform an estimate of the local measurement and to update the free-flow wind speed estimate. We formally prove the convergence of this estimate and numerically illustrate the efficiency of this method.Finally, we move to a more general setup where both the free-flow wind speed and direction are unknown. We propose to use a two-dimensional wake model and to rely on an optimization-based method. This identification problem reveals to be particularly challenging due to the appearance of transport delays, but we illustrate how to circumvent this issue by considering an average value of the free flow wind speed history. Simulation results obtained with the simulator FAST.Farm illustrate the interest of the proposed method
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Haag, Christian. "Temporal and spatial wind field distribution in Delaware Bay." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file 9.11 Mb., 62 p, 2006. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pqdiss&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&rft_dat=xri:pqdiss:1430767.
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Thesis (M.E.E.)--University of Delaware, 2006.Principal faculty advisors: Kenneth E. Barner, Dept. of Electrical and Computer Engineering; and Mohsen Badiey, Dept. of Marine and Earth Studies. Includes bibliographical references.
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Duhaut, Thomas H. A. "Wind-driven circulation : impact of a surface velocity dependent wind stress." Thesis, McGill University, 2006. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=101117.
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The use of an ocean surface velocity dependent wind stress is examined in the context of a 3-layer double-gyre quasigeostrophic wind-driven ocean circulation model. The new wind stress formulation results in a large reduction of the power input by the wind into the oceanic circulation. This wind stress is proportional to a quadratic function of Ua--u o, where Ua is the wind at 10m above the ocean surface and uo is the ocean surface current. Because the winds are typically faster than the ocean currents, the impact of the ocean surface velocity on the wind stress itself is relatively small. However, the power input is found to be greatly reduced with the new formulation. This is shown by simple scaling argument and numerical simulations in a square basin. Our results suggest that the wind power input may be as much as 35% smaller than is typically assumed.The ocean current signature is clearly visible in the scatterometer-derived wind stress fields. We argue that because the actual ocean velocity differs from the modeled ocean velocities, care must be taken in directly applying scatterometer-derived wind stress products to the ocean circulation models. This is not to say that the scatterometer-derived wind stress is not useful. Clearly the great spatial and temporal coverage make these data sets invaluable. Our point is that it is better to separate the atmospheric and oceanic contribution to the stresses.
Finally, the new wind stress decreases the sensitivity of the solution to the (poorly known) bottom friction coefficient. The dependence of the circulation strength on different values of bottom friction is examined under the standard and the new wind stress forcing for two topographic configurations. A flat bottom and a meridional ridge case are studied. In the flat bottom case, the new wind stress leads to a significant reduction of the sensitivity to the bottom friction parameter, implying that inertial runaway occurs for smaller values of bottom friction coefficient. The ridge case also gives similar results. In the case of the ridge and the new wind stress formulation, no real inertial runaway regime has been found over the range of parameters explored.
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SILVA, ILITCH VITALI GOMES DA. "THE WIND FORECAST FOR WIND POWER GENERATION." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2010. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=16824@1.
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CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOA energia eólica é uma das alternativas mais promissoras para geração de energia elétrica, pois assegura a diversidade e segurança no fornecimento de energia e atende à necessidade premente de reduzir os níveis de emissão de gases poluentes. Na operação de sistemas elétricos com forte presença de geração eólica é fundamental prever com pelo menos um dia de antecedência os valores futuros (pelo menos horários) da veloci-dade do vento, pois assim pode-se avaliar a disponibilidade de energia para o próximo dia, uma informação útil no despacho das unidades geradoras e no controle do sistema elétrico. A proposta dessa dissertação objetiva especificamente desenvolver modelos de previsão de curto prazo da velocidade do vento, baseado em técnicas de inteligência artificial, modelo da rede neural artificial e neuro-fuzzy adaptativa (ANFIS) e um mode-lo Estatístico composto por um modelo de regressão harmônica e Box-Jenkins. Para aplicação da metodologia considerou-se o município de São João do Cariri (Estado de Paraíba), onde está localizada uma das estações de referência do projeto SONDA (Sis-tema Nacional de Dados Ambientais para o setor de energia). O desempenho dos mode-los rede neural, neuro-fuzzy (ANFIS) e modelo Estatístico são comparados nas previ-sões de 6 horas, 12 horas, 18 h e 24horas a frente. Os resultados obtidos mostram o me-lhor desempenho da modelagem ANFIS e encorajam novos estudos no tema.
Wind power is one of the most promising options for power generation. It ensures the diversity and security of energy supply and meets the pressing need to reduce the levels of emission of polluting gases. In the operation of electrical systems with a strong presence of wind generation, it is essential to provide at least one day in advance the future values (at least hourly) of wind speed, so that we can assess the availability of energy for the next day, a useful information in the order of the generating units and electrical control system. The purpose of this dissertation aims to develop models spe-cifically to develop models to forecast short-term wind speed, based on artificial intelligence techniques, artificial neural network model and adaptive neuro-fuzzy Systems (ANFIS) and a statistical model composed of a harmonic regression model and Box-Jenkins. For application of the methodology, the city of São João do Cariri (State of Paraíba), where a reference station of SONDA project (National Environmental Data for the energy sector) is located, was considered.To apply the methodology was consi-dered the city of the ray tracing model (State of Paraíba), which is located a station ref-erence design (National Environmental Data for the energy sector). The performance of artificial neural network model and adaptive neuro-fuzzy Systems (ANFIS) and a statis-tical model are compared mixed forecasts of 6 hours, 12 hours, 18hours and 24 hours ahead. The results show the best performance of the ANFIS model and encourage fur-ther studies on the subject.
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Hickle, Curtis. "Wind Tunnel renovation, flow verification and flapping wing analysis." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2006. http://library.nps.navy.mil/uhtbin/hyperion/06Jun%5FHickle.pdf.
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Thesis (M.S. in Mechanical Engineering)--Naval Postgraduate School, June 2006.Thesis Advisor(s):Dr. Kevin Jones and Dr. Garth Hobson. "June 2006." Includes bibliographical references (p.79-81). Also available in print.
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Paul, Matthew G. "Wing Deflection Analysis of 3D Printed Wind Tunnel Models." DigitalCommons@CalPoly, 2017. https://digitalcommons.calpoly.edu/theses/1751.
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This work investigates the feasibility of producing small scale, low aerodynamic loading wind tunnel models, using FDM 3D printing methods, that are both structurally and aerodynamically representative in the wind tunnel. To verify the applicability of this approach, a 2.07% scale model of the NASA CRM was produced, whose wings were manufacturing using a Finite Deposition Modeling 3D printer. Experimental data was compared to numerical simulations to determine percent difference in wake distribution and wingtip deflection for multiple configurations.
Numerical simulation data taken in the form of CFD and FEA was used to validate data taken in the wind tunnel experiments. The experiment utilized a wake rake to measure 3 different spanwise locations of the wing for aerodynamic data, and a videogrammetry method was used to measure the deflection of the wingtips for structural data. Both numerical simulations and experiments were evaluated at Reynolds numbers of 258,000 and 362,000 at 0 degrees angle of attack, and 258,000 at 5 degrees angle of attack.
Results indicate that the wing wake minimum in the wind tunnel test had shifted approximately 8.8mm at the wingtip for the Nylon 910 wing at 258,000 Reynolds number for 0 degrees angle of attack when compared to CFD. Videogrammetry results indicate that the wing deflected 5.9mm, and has an 18.6% difference from observed deflection in FEA. This reveals the potential for small scale wind tunnel models to be more representative of true flight behavior for low loading scenarios.
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Fridén, Tobias. "Robust Autonomous Landing of Fixed-Wing UAVs in Wind." Thesis, Linköpings universitet, Reglerteknik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-165136.
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Fixed-wing UAVs are today used in many different areas, from agriculture to search and rescue operations. Through various research efforts, they are becoming more and more autonomous. However, the procedure of landing a fixed-wing UAV remains a challenging task, which requires manual input from an experienced pilot. This work proposes a novel method which autonomously performs such landings. The main focus is on small and light-weight UAVs, for which the wind acts as a major disturbance and has to be taken into account. Robustness to other disturbances, such as variations in environmental factors or measurement errors, has also been prioritized during the development of this method.The main contribution of this work consists of a framework in which der\-iva\-tive-free optimization is used to calculate a set of waypoints, which are feasible to use in different wind speeds and directions, for a selected UAV model. These waypoints are then combined online using motion planning techniques, to create a trajectory which safely brings the UAV to a position where the landing descent can be initiated. To ensure a safe descent in a predefined area, another nonlinear optimization problem is formulated and solved. Finally, the proposed method is implemented on a real UAV platform. A number of simulations in different wind conditions are performed, and data from a real flight experiment is presented. The results indicate that the method successfully calculates feasible landing sequences in different scenarios, and that it is applicable in a real-world landing.
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Li, Simeng. "WIND ARRAY PERFORMANCE EVALUATION MODEL FOR LARGE WIND FARMS AND WIND FARM LAYOUT OPTIMIZATION." Case Western Reserve University School of Graduate Studies / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=case1405080318.
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Shelley, Dena L. "A wind energy landscape : the Searsburg Wind Park." Virtual Press, 2008. http://liblink.bsu.edu/uhtbin/catkey/1390311.
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Wind Energy facilities are becoming a more common occurrence among the U.S. landscape. The shift to renewable from non-renewable energy sources is an important agenda item for energy policy in the 21st century. Unlike other forms of energy, the unique visual aspects of wind energy provide opportunities to engage with and actually view the process of energy production. The sculptural element of turbines and their placement in highly visible areas, such as mountain ridges, provides opportunities of environmental interpretation and public interaction. Although existing security and safety precautions in the U.S. do not allow public use of these facilities, the integration of turbines into public places is becoming more common in other parts of the world. This creative project focuses on developing dynamic and unique cultural places that also serve as education spaces to celebrate wind and wind energy. Environmental art installations among the wind turbines serve as human-scaled interpretational guides to create meaningful, learning experiences between the user, the wind and the landscape.This project highlights the existing eleven-turbine (6MW) facility in the town of Searsburg in southern Vermont. This project includes inventory, analysis and site design of an existing wind facility. The methodology includes using GIS data and existing sight line data, as well as significant and environmental cultural points. Finally, general guidelines are included as a design foundation for other wind energy facilities.Department of Landscape Architecture
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Moor, Gary Duncan. "Optimization of wind energy transfer using wind turbines." Thesis, Stellenbosch : Stellenbosch University, 2003. http://hdl.handle.net/10019.1/53542.
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Thesis (MScIng)--Stellenbosch University, 2003.ENGLISH ABSTRACT: The effect of topography and terrain on wind is examined in order to ensure that the wind turbine positioning will encourage a greater availability of wind energy to it. Maximum power point tracking methods are presented whereby the loading on the wind turbine is controlled to ensure that the maximum available energy from the wind is captured. The wind turbine system is modelled and used in simulations to evaluate the three proposed maximum power point trackers, named anemometer control, calculation control and constant step control for the purpose of this thesis. An additional analog system is also created whereby the complete wind turbine system is able to be simulated. An inverter is used to replicate the generator and the loading is controlled using an active rectifier since this will be used on the practical system. The results from the simulations and analog system are presented whereby one of the trackers is shown to be inadequate and the other two trackers are shown to be close to ideal. The appeal of the calculation method is in the redundancy of an anemometer making it attractive to less expensive, small-scale systems.
AFRIKAANSE OPSOMMING: Die invloed van die topografie en die terrein op die dinamika van wind word ondersoek om sodoende te verseker dat die posisionering van wind turbienes 'n beter effektiwiteit van wind energie oordrag sal bewerkstellig. Maksimum drywingspunt volger metodes word bespreek sodat die lading op die wind turbiene beheer kan word om sodoende te verseker dat die maksimum wind energie oorgedra kan word. Die wind turbiene stelsel word gemodeleer en geimplimenteer om die drie voorgestelde maksimum drywingspount volgers te evalueer, naamlik windspoedbeheer, berekening-beheer en konstantestap-beheer vir die doeleindes van hierdie tesis. 'n Adissionele analoog stelsel is ontwerp waarmee die volledige wind turbiene stelsel gesimuleer kan word. 'n Omsetter word gebruik om die generator na te boots en die belading word beheer deur middel van 'n aktiewe gelykrigter soos gebruik 'n praktese stelsel. Resultate van die simulasies en die analog stelsel is verskaf om te bewys dat een van die volg-metodes onvoldoende volging bewerkstellig, en die ander twee nabyaan ideale volging bewerkstellig. Dit is getoon dat die berekening metode meer aantreklik is vir kleinskaal stelsels, aangesien 'n windspoedsensor onnodig is.
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Eriksson, Petersen Lovisa. "The impact of wind conditions on wind turbines." Thesis, KTH, Energiteknik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-192535.
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The world is facing global warming and the challenge to reduce greenhouse gas emissions. Wind power is a renewable source of energy with no greenhouse gas emissions when operating. Therefore, it could contribute in this challenge. Vattenfall is a Swedish energy company that invests in the wind power business and have many wind turbines in operation. On behalf of Vattenfall this study has been performed with the aim to find how wind conditions affect wind turbines and how it is correlated to amount of alarms, time loss, energy availability and time availability in a wind turbine. Improving this knowledge will be an advantage when making investments in wind turbines and their maintenance. A statistical analysis was conducted in order to examine correlations of wind speed and turbulence intensity with the number of alarms, time loss, energy availability and time availability of a turbine. A case study of Lillgrund, an offshore park in Sweden, was performed since the park layout is tightly spaced and hence interesting in sense of turbulence intensity. Lillgrund suffered to a lot of blade vibration alarms and therefore these alarms were investigated deeper in terms of the wind conditions one hour, one day and one week before the alarm occurred. Four additional parks with other turbine types and manufacturers than Lillgrund’s were also included in the correlation analysis. The amount of alarms per year of each turbine was examined in order to compare this with the failure curve of a wind turbine. The purpose was to see if the wear-out period had started earlier for turbines with certain wind conditions but unfortunately the turbines were not old enough to draw a conclusion. The analysis resulted in positive correlations for high turbulence and high amount of alarms and blade vibration alarms for the Siemens SWT-2.3-93 turbines investigated while there were no clear correlations for time loss, energy availability and time availability. Also, the other turbine types had no strong correlations for the investigated parameters. From the results it can be concluded that there are no strong correlations for the wind conditions investigated and energy availability and time availability. It can also be said that the amount of alarms in Siemens SWT-2.3-93 turbines increases with higher turbulence. Hence, alarms do not influence the energy availability noticeably for this type of turbine.Världen står inför en global uppvärmning och utmaningen att minska utsläppen av växthusgaser. Vindkraft är en förnybar energikälla utan utsläpp av växthusgaser vid drift som skulle kunna bidra positivt i denna utmaning. Vattenfall är ett svenskt energiföretag som investerar i vindkraftsverksamhet och äger många vindkraftverk. Denna studie genomförts på uppdrag av Vattenfall med syfte att finna hur vindförhållanden påverkar vindkraftverk och hur de är korrelerade till mängden av alarm, tidsförlust, energitillgänglighet och tidstillgänglighet i ett vindkraftverk. Att förbättra denna kunskap kommer att vara en fördel när investeringar i vindkraftverk och deras underhåll görs. En statistisk analys genomfördes för att undersöka korrelationer av vindhastighet och turbulensintensitet med antalet alarm, tidsförlust, energitillgänglighet och tidstillgänglighet hos en turbin. En studie av Lillgrund, en havsbaserad park i Sverige, genomfördes då parkens turbiner är placerade tätt intill varandra och därmed ger ett intressant perspektiv på turbulensintensitet. Lillgrund har en stor mängd bladvibrationsalarm och därför har dessa alarm undersökts djupare när det gäller vindförhållandena en timme, en dag och en vecka innan alarmet inträffade. Ytterligare fyra parker med andra turbintyper och tillverkare än Lillgrunds ingick i korrelationsanalysen. Mängden alarm per år för varje turbin undersöktes för att jämföra detta med felintensitetskurvan för ett vindkraftverk. Syftet var att se om utslitningsperioden hade börjat tidigare för turbiner med vissa vindförhållanden men tyvärr var de studerade turbinerna inte tillräckligt gamla för att dra slutsatser kring detta. Analysen resulterade i positiva korrelationer för hög turbulens och hög mängd av alarm och bladvibrationsalarm för de undersökta Siemens SWT-2.3-93-turbinerna medan det inte fanns några tydliga korrelationer för tidsförlust, energitillgänglighet och tidstillgänglighet. Även de andra turbintyperna saknade starka samband för de undersökta parametrarna. Av resultaten kan slutsatsen dras att det inte finns några starka samband för de undersökta vindförhållandena och energitillgängligheten och tidstillgängligheten. Det kan också sägas att mängden alarm i Siemens SWT-2.3-93-turbiner ökar med högre turbulensintensitet. Därför påverkar inte alarm energitillgängligheten märkbart för denna typ av turbin.
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Marshall, Bryan Jonathan. "Wind flow structures and wind forces in forests." Thesis, University of Oxford, 1998. http://ora.ox.ac.uk/objects/uuid:16f42b9c-a87c-43f9-bcc3-def409aa61d5.
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This thesis describes a series of 1:75 scale wind tunnel experiments investigating the wind flow over, and through, three different forest models and the resultant wind loading on individual model trees. The experiments were designed to lead to a quantitative assessment of the wind stability of the particular forest arrangements and also to permit a study of the coherent gust structures in the flow. Forest canopy flow is dominated by a plane mixing layer flow regime with a shear layer close to the canopy top. It has been confirmed that data can be correlated usefully in terms of a shear length, Ls, related to the form of this shear layer. Frequency analysis has confirmed that the flow structures have the same frequency as the swaying of the tallest trees in each forest. A mechanism is proposed whereby upstream turbulence induces swaying of trees at and near the upwind edge region of the forest, which in turn perturbs the air in the unstable shear layer. This leads to a roll-up of the shear layer and the creation of coherent flow structures. Conditional sampling of the gust structures, using wavelet analysis, has also supported the theory of a plane mixing layer type flow. An eddy-pair structure was revealed, the arrangement of which accounts for the intermittent strong downward sweeps of air into the canopy that have been reported by many observers. The large downward sweep of air was also shown to be responsible for the highest bending moments experienced by individual trees. Assessments of the different forest formations showed that in a forest consisting of a 50/50 mix of 200 mm and 100 mm model trees, gusts did not penetrate the lower forest. This arrangement should improve the protection of younger trees and may be worth investigating in field trials.
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Makhalas, Kharsan Al, and Faisal Alsehlli. "Wind Power." Thesis, Blekinge Tekniska Högskola, Institutionen för tillämpad signalbehandling, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-4336.
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This Bachelor thesis has been written at the Blekinge Institute of Technology. This thesis concentrates on the wind power and their components, also the large wind farm is studied. The electrical power is generated by using the power in wind to drive a wind turbine to produce mechanical power. This mechanical power can be converted into electrical power by using electrical induction generators. There are two types of the wind turbines, the horizontal axis and vertical axis wind turbine, where the horizontal axis wind turbine is mostly used and was studied in this thesis. The rotor can be placed in two directions: an upwind rotor where the blade of turbine faces to the wind, so it operates more smoothly and transmit more power. The other type is a downwind rotor which orients itself with respect for the wind direction. Moreover, the tower shadow makes the blade to flex, consequently resulting in fatigue, noise, and reduces output of the power. The modern wind turbine has been built with an odd number of blades which is important for the stability of the turbine. The rotor with an odd number of blades can be considered to be similar to a disc when calculating the dynamic properties of the machine. The main idea of this thesis is to study the wind power in general and large wind parks specifically. The Horns Rev wind park was taken as an example of a wind park in Denmark and the Gotland wind park as an example of a wind park in Sweden too. Into account, the distance between wind turbine in the wind direction cannot be too small. If the wind turbines are located to close to each other, the wind will be more and more turbulent after it passes through each single wind turbine. This would lead to that wind turbines downstream in the wind park, and it might even have to shut down due to that mechanical loading gets to high during strong conditions. This is due to the fact that when wind passes through the rotor of the wind turbine it gets very turbulent and the wind speed is decreased. The minimum length of the rotor should be approximately 5-7 rotor diameters to avoid that issue. Gotland Energy AB (GEAB) considered, that high voltage direct current light would be the only realistic way to solve the technical problems for the high amount of wind power in-feed. One result is that The stability of voltage during transient events, has become much better by using the high voltage direct current light so that the output current stability from the asynchronous generators have been improved, which reduces the stresses on the AC grid and on the mechanical construction of the windmills.In general the wind turbines with three blades accommodated a thicker root are used. It is obvious that, the less number of blades on the wind turbine, the cost of material and manufacturing will be lower. It is worthy to mentioned that, the modern wind turbine has been built with an odd number of blades. When the length of the blade increases the deflection of blade tip due to axial wind force also increase as well. So without consider the increase in length of blade may lead to dangerous situation of collision of tower and blade. Moreover, by increasing the number of blades cost of the system would increased as well. The limit of transfer for the AC transmission system depends on the distance from shore and is therefore physically limited by this. AC large wind parks that are placed at a long distance from the shore, which means AC long transmission line, and more drop voltage A solution to AC long transmission line, it could be to decrease the offshore frequency and use a low frequency AC networks. There is a suggestion by for instance (Schütte, Gustavsson and Ström 2011). The usages of a low frequency system are in electrified railway systems, where the frequency ranges from 16.67 Hz to 25 Hz. However, the network of a low frequency would allow a simpler design of the offshore WTs and The aerodynamic rotor of a large WT operates at maximum revolutions at 15-20 rpm. The lower frequency would then allow a smaller gear ratio for turbines with a gearbox, or decrease the poles number for WTs with direct driven generators. This would lead to lighter and cheaper turbines. One of the disadvantages by using a low frequency system is the size of transformer would be increased, and hence, the costs of transformer will increased too. The operator of the grid, Gotland Energy AB (GEAB) considered, that HVDC light would be the only realistic way to solve the technical problems for the high amount of wind power in-feed. The experiences have supported expected improvements in the characteristics for example: - Stability in the system arose. - Reactive demands, power flows, as well as voltage level in the harmonic and system were reduced. - Flicker problems were eliminated with the installation of HVDC light and transient phenomena disappeared. Moreover, Overall experiences of Gotland Energy AB (GEAB) are that the control of power flow from the converters makes the AC grid easier to observe than a conventional AC network and the power variations do not stress the AC grid as much as in normal network. Voltage quality has been better with the increased wind power production. A topic to study in the future is the consequences of blackouts in power supply with many wind power farm.
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Kimm, Dennis. "Windy Business: Exploring a Local Wind Power Project in Germany." Thesis, Uppsala universitet, Institutionen för geovetenskaper, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-330950.
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The need for a sustainable energy supply is widely recognized, as formulated under goal 7 of the United Nations’ Sustainable Development Goals. Yet, on the local level problems may arise with the implementation of renewable energy systems, such as wind power. Issues around visual intrusion of the landscape, noise and shadow flicker, and concerns over wildlife protections are often in the heart of local resistance to wind power projects. The aim of this thesis is to closely examine the developments for wind power in the city of Euskirchen in Germany, including the planning and decision making processes, with regards to milestones and obstacles encountered over the last two decades. The analysis applies the methodology of a qualitative case study. Furthermore, views and opinions of involved and affected parties are collected through semi-structured interviews, and analysed through the lenses of social acceptance and public participation. Finally, from the examination of the planning and decision making processes and the discovered local attitudes towards wind energy, recommendations will be formulated to guide future wind power developments in the region.
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Engel, Mark A. "A wind tunnel investigation of a wing-tip trailing vortex." Thesis, This resource online, 1995. http://scholar.lib.vt.edu/theses/available/etd-01102009-063459/.
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Thomas, Joel. "COMPARATIVE ANALYSIS OF WIND ATLASES: WIND RESOURCE ASSESSMENT OF FORESTED SITES FOR WIND POWER DEVELOPMENT." Thesis, Uppsala universitet, Institutionen för geovetenskaper, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-448544.
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Wind atlases are interactive databases used extensively for preliminary wind resource assessment aimed at optimal wind power development. The selection and processing of wind atlas data are important and will determine the quality of the subsequent WRA (Wind Resource Assessment) phases. This study aims to compare, process, and interpret different wind atlases in determining effective wind resource analysis for 14 different sites in Sweden. The wind atlas data is accessed, parsed, and compared using multiple methodologies to ensure a fair comparison. Several variables like wind speed, wind direction, temperature, production values, etc. are analysed and compared amongst the wind atlas data. The corrected versions of the data are drawn out to conclude and determine how well those databases represent the realistic conditions in a forested site. The data is also compared and validated with measurement data. The results indicate several layers of insights into the wind resource regime. The preliminary results from 14 sites show that New European Wind Atlas (NEWA) and Global Wind Atlas (GWA) agreed sufficiently on the subject of the wind conditions for most of the sites. Methodologies like downscaling and long-term correction introduced to the wind atlas data provided more insights and proved that the database could expand and include more complex wind conditions in the coming years. Furthermore, the comparison and analysis of wind atlas data along with measurement data revealed that NEWA aligned the most to the actual wind conditions for a site. Several uncertainties are considered but more validation and thorough insights in the future could determine and give more affirmations to the idea put forward. Further studies could be conducted along with the inclusion of additional layers, variables, and databases to the wind atlases.
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Kelley, Owen A. "The association of tall eyewall convection with tropical cyclone intensification." Fairfax, VA : George Mason University, 2008. http://hdl.handle.net/1920/3073.
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Thesis (Ph.D.)--George Mason University, 2008.Vita: p. 320. Thesis director: Michael Summers. Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Computational Sciences and Informatics. Title from PDF t.p. (viewed July 3, 2008). Includes bibliographical references (p. 291-319). Also issued in print.
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Steiln, Oliver [Verfasser]. "Regen-Wind induzierte Schwingungen im natürlichen Wind / Oliver Steiln." Aachen : Shaker, 2015. http://d-nb.info/1098039351/34.
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Mason, Jesse Cheyenne. "On improving wind-turbine hub-height wind-speed forecasts." Thesis, University of British Columbia, 2014. http://hdl.handle.net/2429/46558.
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Weekes, Shemaiah Matthias. "Small-scale wind energy : methods for wind resource assessment." Thesis, University of Leeds, 2014. http://etheses.whiterose.ac.uk/6413/.
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Small-scale wind energy is a renewable energy technology with exciting prospects in a low carbon energy future. However, in order for the technology to be fully utilized, techniques capable of predicting the wind energy resource quickly, cheaply and accurately are urgently required. Specifically, the direct measurement approaches used in the large-scale wind industry are often not financially or practically viable in the case of small-scale installations. The subject of this thesis is the development of low-cost, indirect methods for predicting the wind resource using, (i) analytical models based on boundary layer meteorology and (ii) data-driven techniques based on measure-correlate-predict (MCP). The approaches were developed and tested using long-term (11 years) wind data from meteorological stations, short-term (1 year) data from a field trial of small-scale turbines, and output from an operational forecast model. As a first step, the performance of an existing boundary layer scaling model was evaluated at 38 UK sites and found to result in large site-specific errors. Based on these findings, a revised model was developed and shown to improve prediction accuracy. However, uncertainty analysis and comparison with onsite measurements revealed average errors in the predicted wind power density of over 60% due to uncertainties in the model input parameters. Hence, it was concluded that such an approach is best applied in a scoping context to identify sites worthy of further study. To investigate the ability of low-cost, data-driven techniques to reduce these uncertainties, MCP approaches were trialled using onsite measurement periods as short as 3 months at a subset of 22 of the above UK sites. In addition to established linear approaches, non-linear Gaussian process regression and bivariate conditional probability approaches were developed. Using a 3 month measurement period, the best performing MCP approaches resulted in average errors in the predicted wind power density of 14%, compared to 26% when using the boundary layer scaling approach at the same sites. The effect of seasonal variability in the prediction errors was investigated in detail and found to be most significant at coastal sites. This variability was found to be reduced by using output from an operational forecast model in place of long-term reference wind data. This work provides a means for low-cost and rapid wind resource assessment in cases where traditional approaches are not viable.
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Soler-Bientz, Rolando. "Evaluation of the wind patterns over the Yucatán Peninsula in México." Thesis, Loughborough University, 2010. https://dspace.lboro.ac.uk/2134/5988.
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Wind power is seen as one of the most effective means available to combat the twin crises of global climate change and energy security. The annual market growth has established wind power as the leading renewable energy technology. Due to the availability of sparsely populated and flat open terrain, the Yucatán Peninsula located in eastern México is a promising region from the perspective of wind energy development but no comprehensive assessment of wind resource has been previously published. A basic requirement when developing wind power projects is to study the main characteristic parameters of wind in relation to its geographical and temporal distribution. The analysis of diurnal and seasonal wind patterns are an important stage in the move towards commercial exploitation of wind power. The research developed during the PhD has comprehensively assessed the wind behaviour over the Yucatán Peninsula region covering long term patterns at three sites, a spatial study using short term data for nine sites, a vertical profile study on one inland site and an offshore study made on a pier at 6.65km from the North shore. Monthly trends, directional behaviours and frequency distributions were identified and discussed. The characteristics of the wind speed variation reflected their proximity to the coast and whether they were influenced by wind coming predominantly from over the land or predominantly from over the sea. The atmospheric stability over the eastern seas was also analysed to assess thermal effects for different wind directions. Diurnal wind speed variations are shown to be affected in particular by the differing wind conditions associated with fetches over two distinct offshore regions. Seasonal behaviour suggests some departure from the oscillations expected from temperature variation. The offshore wind is thermally driven suggesting largely unstable conditions and the potential development of a shallow Stable Internal Boundary Layer.
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Dahmer, Marc R. Market Patrick S. "Investigating near-surface wind fields as influenced by low-level jet occurrences in Missouri." Diss., Columbia, Mo. : University of Missouri--Columbia, 2009. http://hdl.handle.net/10355/6555.
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The entire thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file; a non-technical public abstract appears in the public.pdf file. Title from PDF of title page (University of Missouri--Columbia, viewed on November 13, 2009). Thesis advisor: Dr. Patrick S. Market Includes bibliographical references.
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Laupattarakasem, Peth. "An Improved Hurrican Wind Vector Retrieval Algorithm Using Sea Winds Scatterometer." Doctoral diss., University of Central Florida, 2009. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/2522.
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Over the last three decades, microwave remote sensing has played a significant role in ocean surface wind measurement, and several scatterometer missions have flown in space since early 1990's. Although they have been extremely successful for measuring ocean surface winds with high accuracy for the vast majority of marine weather conditions, unfortunately, the conventional scatterometer cannot measure extreme winds condition such as hurricane. The SeaWinds scatterometer, onboard the QuikSCAT satellite is NASA's only operating scatterometer at present. Like its predecessors, it measures global ocean vector winds; however, for a number of reasons, the quality of the measurements in hurricanes are significantly degraded. The most pressing issues are associated with the presence of precipitation and Ku-band saturation effects, especially in extreme wind speed regime such as tropical cyclones (hurricanes and typhoons). Under this dissertation, an improved hurricane ocean vector wind retrieval approach, named as Q-Winds, was developed using existing SeaWinds scatterometer data. This unique data processing algorithm uses combined SeaWinds active and passive measurements to extend the use of SeaWinds for tropical cyclones up to approximately 50 m/s (Hurricane Category-3). Results show that Q-Winds wind speeds are consistently superior to the standard SeaWinds Project Level 2B wind speeds for hurricane wind speed measurement, and also Q-Winds provides more reliable rain flagging algorithm for quality assurance purposes. By comparing to H*Wind, Q-Winds achieves ~9% of error, while L2B-12.5km exhibits wind speed saturation at ~30 m/s with error of ~31% for high wind speed (> 40 m/s).Ph.D.
School of Electrical Engineering and Computer Science
Engineering and Computer Science
Electrical Engineering PhD
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Allan, Mark. "A CFD investigation of wind tunnel interference on delta wing aerodynamics." Thesis, University of Glasgow, 2002. http://theses.gla.ac.uk/4081/.
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To explore the influence of wind tunnel test facilities on delta wing aerodynamics, the interference has been separated into two distinct types, wall interference and support structure interference. The wall interference effects have been split into three further components, tunnel blockage, side wall interference, and roof and floor interference. Splitting the tunnel influence in this way allows us to determine the most detrimental interference effects, thus allowing the wind tunnel engineer to design experiments accordingly. Euler and more realistic RANS simulations of tunnel interference have been conducted. To reduce the question of grid dependence when comparing solutions, a common "farfield grid" was created and tunnel grids were extracted. Before doing RANS simulations an analysis of various turbulence models was conducted. It was found that turbulence models have difficulty in predicting turbulence levels in leading edge vortices. As such modifications have been applied to the models which improve predictions. Despite vortex breakdown being widely regarded as an inviscid phenomenon, dependence on turbulence modelling has been exhibited. This is due to the vortex properties being altered with turbulent diffusion of vorticity when turbulence levels are too high. Both 1- and 2-equation models were assessed and it was concluded that a modified 2-equation k-w model was the most suitable of the models available (when compared against experimental results), and was therefore used in all subsequent simulations. From both Euler and RANS simulations it has been concluded that the effect of sidewall proximity significantly promotes vortex breakdown. Side wall induced velocity components increase the mean effective incidence of the wing, the helix angle and the strength of the vortices. The combination of these effects promotes vortex breakdown. Roof and floor proximity has little effect on vortex breakdown as does the frontal area blockage. Pitching simulations have shown that the promotion of vortex breakdown is not consistent on both the upstroke and downstroke. Break-down was observed to be prompted furthest at the higher incidence of the upstroke and on the downstroke. This highlights the dependency of tunnel interference on vortex strength.
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Kuhlman, Christopher J. "Evaluation of convective wind forecasting methods during high wind events." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2006. http://library.nps.navy.mil/uhtbin/hyperion/06Mar%5FKuhlman.pdf.
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Lubitz, William David. "Near real time wind energy forecasting incorporating wind tunnel modeling /." For electronic version search Digital dissertations database. Restricted to UC campuses. Access is free to UC campus dissertations, 2005. http://uclibs.org/PID/11984.
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Garber, Jason. "Wind loads on and wind-induced overturning of container cranes." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0005/MQ42064.pdf.
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Conan, Boris. "Wind resource accessment in complex terrain by wind tunnel modelling." Phd thesis, Université d'Orléans, 2012. http://tel.archives-ouvertes.fr/tel-00843645.
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To benefit from strong winds, an increasing number of wind turbines are placed in complex terrains. But complex terrains means complex flows and difficult wind resource assessment. This study proposed to use wind tunnel modelling to evaluate the wind in a complex topography. The goal of this study is to evaluate the possibilities of wind resources assessment by wind tunnel modelling and to quantify the important modelling parameters. The lower part of the atmosphere, the atmospheric boundary layer (ABL) is defined by a velocity and a turbulence gradient. The ABL is reproduced in the wind tunnel by placing obstacles and roughness elements of different size representative to the type of terrain desired. The flow produced in the wind tunnel is validated against field data and a wise choice of the obstacles is discussed to reproduce the desired wind profile. The right reproduction of the inflow conditions is found to be the most important parameter to reproduce. The choice of the area to reproduce around a site in usually difficult to make in order to keep a low scaling factor and to account for the surrounding topography. A series of tests on simplified hills helps the experimentalist in this choice by enlightening the longitudinal and vertical extension of the wake downstream different hills shapes. Finally, two complex topographies are studied in two wind tunnels, the Bolund hill in Denmark and the Alaiz mountain in Spain. The results are giving good results, 5 to 10 %, for predicting the wind speed but more scatter is observed for the modelling of the turbulence, up to 100 %. The laboratory simulation of atmospheric flows proves to be a demanding but reliable tool for the prediction of the mean wind speed in complex terrain.
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Heidenreich, Sara. "Blowing in the wind : The socialization of offshore wind technology." Doctoral thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for tverrfaglige kulturstudier, 2014. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-27088.
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The development of renewable energy technologies is a widely acknowledged strategy to address climate change. However, for a successful implementation of technology, socialization, i.e. embedding the technology into society, is crucial. This thesis deals with the socialization of the emerging offshore wind technology in Norway. In particular, it focuses on two potential agents of socialization, news media and scientists. The first paper, Dingpolitik at Sea: Offshore wind energy in the news media discourse, focuses on news media as socialization agents. Siting renewable energy offshore is often considered a solution to implementation problems onshore, as it is “out of sight, out of mind”. By analyzing the Norwegian news media discourse on offshore wind energy, this paper investigates whether moving wind turbines at sea really prevents controversy. It finds that although media coverage is largely positive, still, offshore wind energy is contested mainly within economic, environmental and moral frameworks. Further, values and concerns rather than facts are contested in the media debate, while the technology, in its physical form, is blackboxed. The second paper, Sublime technology and object of fear: Offshore wind scientists assessing publics, and the third paper, Outreaching, outsourcing, and disembedding: How offshore wind scientists consider their engagement with the public, address offshore wind scientists as socialization agents. They study the scientists’ imaginings of the public(s) and their socialization strategies. The findings indicate that the scientists construct ambivalent narratives about the public(s). The continued presence of narratives of a negative public in the context of a technology that is supposed to be “out of sight, out of mind,” could be understood as an act of othering the public. Moreover, most scientists did not embrace their role as agents of socialization. Rather, the strategies of outsourcing the socialization to other actors and of disembedded technology development, i.e. declaring socialization unnecessary, are common. The thesis highlights the important role of the media both as agent of and arena for socialization. Furthermore, considering the hesitance among scientists to act as agents of socialization, it suggests that other actors may be more suitable agents of socialization. It also points to the significance of the “out of sight, out of mind” motive which is used to construct socialization as irrelevant and disembed technology development. Hence, the new trend to produce renewable energy at sea may present new challenges for its socialization.Utvikling og utbygging av ny fornybar energiteknologi er allmenn anerkjente strategier for å bekjempe klimaendringene. Men for å få til en vellykket implementering, er sosialisering, dvs. forankring av teknologien i samfunnet, avgjørende. Denne avhandlingen tar for seg sosialiseringen av ny offshore vindteknologi i Norge, og fokuserer på to potensielle sosialiseringsagenter, nyhetsmedier og forskere. Den første artikkelen, Dingpolitik at Sea: Offshore wind energy in the news media discourse, fokuserer på nyhetsmedier som sosialiseringsagenter. Plassering av fornybar energi til havs betraktes ofte som en løsning på implementeringsproblemer på land, siden teknologien da er "ute av syne, ute av sinn". Ved å analysere den norske mediediskursen rundt offshore vindkraft, undersøker artikkelen om det virkelig er ukontroversielt å flytte vindturbinene til havs. Den viser at selv om mediedekningen av temaet i stor grad er positivt vinklet, er offshore vindkraft likevel omstridt, særlig innenfor økonomiske, miljømessige og moralske rammer. Videre er det gjerne verdier og bekymringer snarere enn fakta som diskuteres i mediedebatten, mens teknologien, i sin fysiske form, forblir skjult i en «svart boks». Den andre artikkelen, Sublime technology and object of fear: Offshore wind scientists assessing publics, og den tredje artikkelen, Outreaching, outsourcing, and disembedding: How offshore wind scientists consider their engagement with the public, fokuserer på offshore-vind-forskere som sosialiseringsagenter. Artiklene analyserer forskernes sosialiseringsstrategier og deres forestillinger av allmennheten. Funnene tyder på at forskerne konstruerer ambivalente fortellinger om allmennheten. At det stadig knyttes historier om en negativ allmennhet til en teknologi som er ment å være "ute av syne, ute av sinn", kan ses på som en fremmedgjøring av allmennheten. Svært få forskere påtok seg rollen som sosialiseringsagenter, snarere var det vanlig å overlate sosialiseringen til andre aktører, eventuelt å forstå teknologiutvikling som uavhengig av samfunnet og allmennheten. Avhandlingen belyser den viktige rollen mediene har både som arena for sosialisering og som sosialiseringsagenter. Med bakgrunn i at forskerne nøler med å ta på seg oppgaven som sosialiseringsagenter, foreslår avhandlingen at andre aktører kan være bedre egnete til å sosialisere teknologien. Den peker også på viktigheten av "ute av syne, ute av sinn"-motivet, som brukes til å konstruere sosialisering som irrelevant, og til å løsrive teknologiutviklingen fra samfunnet. På den måten kan den nye trenden å produsere fornybar energi til havs skape nye utfordringer for sosialiseringen av teknologiene.
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Lee, Kwang Hyun. "Responses of floating wind turbines to wind and wave excitation." Thesis, Massachusetts Institute of Technology, 2005. http://hdl.handle.net/1721.1/33564.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Ocean Engineering, 2005.Includes bibliographical references (leaf 55).
The use of wind power has recently emerged as a promising alternative to conventional electricity generation. However, space requirements and public pressure to place unsightly wind turbines out of visual range make it desirable to move large wind farms offshore and into deeper coastal waters. A necessary step for the deployment of wind turbines into deeper waters is the development of floating platform systems. This thesis will present a general technical description of two concept designs for floating wind turbine systems, and make a preliminary evaluation of their performance in wind and waves. A new approach to computing the nonlinear wave excitation is also presented.
by Kwang Hyun Lee.
S.M.
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Oliveira, Henrique Balona de Sá. "Wind erosion of biochar-amended soil: a wind tunnel experiment." Master's thesis, Universidade de Aveiro, 2014. http://hdl.handle.net/10773/14312.
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Mestrado em Engenharia do AmbienteBiochar application to soils has been reported in the scientific community as a possible means of improving agricultural productivity and, at the same time, as a powerful tool for carbon sequestration and climate change mitigation. However, current knowledge of biochar effects on soil functions and possible environmental threats is still not enough for a full-scale implementation. Erosion is one of the most serious and irreversible threats to soil and there is still no information if biochar may increase or decrease soil erosion rates. Soil erosion by wind is of particular interest for biochar, because of the low particle density and potential human exposure. The purpose of this study was to fill this knowledge gap by investigating the wind erosion potential of biochar-amended soil with a focus on the effect of soil moisture content, using a laboratory wind tunnel. Firstly, experimental tests were implemented in the DAO wind tunnel to define a robust wind erosion methodology in a facility only used for smoke studies. Sediment collecting methods, dust fraction analysis and wind velocity range were the main factors that required investigation. The erosion of biochar-amended soil (10% m m-1) and control soil (sandy soil) was simulated by positioning a tray divided in a sample area and an area for creeping particles, inside the test section of the wind tunnel. To determine the effect of soil moisture content on the erosion potential, four moisture contents were used: 0.2%, 1.7%, 4% and 8% (gravimetric). The wind tunnel simulations were performed with the duration of 15 minutes at a wind velocity of 7 m s-1. The samples of collected sediment were oven-dried and weighed to give the sediment loss as consequence of the erosion event. Results on the erosion simulations for control and biochar-amended soil with the wind flow velocity of 7 m s-1 (small erosion event) indicated that only biochar particles were displaced. Erosion of biochar-amended soil was similar for 0.2%, 1.7% and 4.0% and despite a sediment loss reduction of 50% from 4% MC to the higher MC, 8%, this latter was not identified as the threshold MC for the moment when erosion ceases to exist. As for mineral particles, after 4% MC there was no sediment collected indicating this MC as the threshold, even though a reduced mass of particles eroded for the smaller MCs. Further future tests are needed to build a more comprehensive understanding of wind erosion of biochar-amended soils. Relevant factors to include are: higher wind velocities representative of medium and high erosion events, as well as higher MCs to identify when erosion of biochar particles will stop completely. Secondly, based on the results found in the present study, other soil types and biochar types warrant further investigation. Studies like this contribute for the understanding of the effects of biochar application to soil functions, as well as the behaviour and fate of this material, which are indispensable for the development of adequate biochar regulations and policies.
A aplicação de biochar no solo tem sido referida na comunidade científica como um possível meio para melhorar a produtividade agrícola e, ao mesmo tempo, como um instrumento para sequestro de carbono e mitigação de alterações climáticas. Contudo, o conhecimento actual sobre os efeitos do biochar nas funções do solo e possíveis ameaças ambientais não é, ainda, suficiente para uma implementação em larga escala. A erosão é uma das mais sérias e irreversíveis ameaças ao solo e não existe, ainda, informação se o biochar pode aumentar ou reduzir os níveis de erosão. A erosão do solo pelo vento é de particular interesse para o biochar, devido à reduzida densidade das partículas e à potencial exposição humana. O objectivo deste trabalho foi preencher esta falha ao investigar o potencial de erosão do solo melhorado com biochar com enfoque no efeito do teor de humidade, usando um túnel de vento. Primeiramente, testes experimentais foram implementados no túnel de vento do DAO para definir uma metodologia robusta de erosão eólica numa estrutura, até então, apenas usada para estudos de dispersão de poluentes. A colecta do sedimento, análise de fracção de poeiras e a gama de velocidades foram os factores principais que necessitaram de investigação. A erosão de solo com biochar (10% m m-1) e de solo de controle (solo arenoso) foi simulada posicionando um tabuleiro dividido em área de amostra e área para partículas de rolamento, dentro da secção de teste do túnel de vento. Para determinar o efeito do teor de humidade do solo no potencial de erosão, quatro teores de humidade foram usados: 0.2%, 1.7%, 4% and 8% (gravimétricos). As simulações no túnel de vento foram realizadas com a duração de 15 minutos a uma velocidade do vento de 7 m s-1. As amostras de sedimento colectado foram secas e pesadas para fornecerem a perda de sedimento como consequência do evento de erosão. Os resultados das simulações de erosão para o controle e o solo melhorado com biochar, com a velocidade de 7 m s-1 (reduzido evento de erosão) indicaram que apenas partículas de biochar foram movidas. Erosão de solo com biochar foi semelhante para 0.2%, 1.7% and 4.0% e, apesar da redução da perda de sedimento em 50% do teor de 4% para para o teor mais alto, 8%, este último não foi identificado como sendo o limiar para o momento em que a erosão deixa de existir. Relativamente às partículas minerais, após o teor de 4% não houve sedimento colectado indicando este teor de humidade como o limiar, ainda que uma massa reduzida de partículas tenha sofrido erosão para teores mais reduzidos. Testes futuros são necessários para gerar um melhor conhecimento acerca de erosão de solo com biochar pelo vento. Factores relevantes a incluir são: maiores velocidades do vento, representativas de eventos de erosão médios e elevados, tal como maiores teores de humidade para identificar quando a erosão de partículas de biochar pára por completo. Em segundo lugar, com base nos resultados observados neste estudo, outro tipos de solo e biochar impõe mais investigação.Estudos como este contribuem para perceber os efeitos da aplicação de biochar nos solos, bem como o comportamento e destino deste material, que são indispensáveis para o desenvolvimento de regulamentos e políticas adequadas sobre biochar.
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Walgern, Julia. "Impact of Wind Farm Control Technologies on Wind Turbine Reliability." Thesis, Uppsala universitet, Elektricitetslära, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-388333.
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Cost efficient operation and maintenance strategies are crucial for reducing cost of wind energy. Since the regime change from feed-in tariffs to an auction-based bidding system for capacity in most European wind projects, levelized cost of energy is challenged constantly. Therefore, new technologies such as new controllers are developed to improve operation and to increase profit. Previous research studies demonstrated the advantage of increased power output of wake redirection control. However, understanding and quantifying the impact of wind farm control technologies on operation and maintenance strategies is inevitable to evaluate the economic feasibility of such new technologies. Thus, an event-based O&M simulation tool has been developed. Besides general modules, such as the wind turbine model, the weather forecasting model and a model for simulating corrective and planned maintenance, the developed tool also takes wake effects into account. This allows considering different power productions for each individual turbine and a failure rate distribution within the wind farm which is based on altering loads on the different components. Both aspects are driven by changes in operation when applying a new controller technology. Exemplarily, the economic feasibility of a closed-loop active wake steering control has been analysed. Main achievements of this study are the possibility to quantify the impact of the active wake steering control on O&M related KPIs. Results show that additional loads caused by applying yaw-misalignment and redirecting wake, lead to an increase in OPEX. However, the achieved energy production gain and thus related additional revenue exceeds additional cost in the case study. Nonetheless, the study reveals that the profitability of the controller is highly dependent on the electricity price which can be acquired during the wind farm’s lifetime.
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Stival, Leandro Jose Lemes. "A study on wind assessment on the wind power performance : wind shear and turbulence intensity effects besides the wake modeling for a single wind turbine." reponame:Repositório Institucional da UFPR, 2017. http://hdl.handle.net/1884/49088.
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Orientador : Prof. Dr. Alexandre Kolodynskie GuetterCoorientador : Prof. Dr. Fernando Oliveira Andrade
Dissertação (mestrado) - Universidade Federal do Paraná, Setor de Tecnologia, Programa de Pós-Graduação em Engenharia de Recursos Hídricos e Ambiental. Defesa: Curitiba, 04/04/2017
Inclui referências : f.91-97
Resumo: A energia eólica cresceu significativamente, porém a eficiência de geração da fonte eólica gira em torno de 30% da energia cinética disponível no vento. Por este motivo é de extrema importância que estudos sejam elaborados afim de aumentar a eficiência na geração de energia. Este estudo visa investigar odesempenho da geração de energia eólica em dois parques eólicos situadosna América do Norte, através da investigação dos dados de vento e modelagem da esteira turbulenta. Os dados analisados são provenientes da turbina, SCADA, e dados coletados pelo LiDAR. A partir das análises dos dados de vento foram estimados parâmetros como tensão de cisalhamento do vento, rosa dos ventos, perfil de velocidade do vento e intensidade de turbulência. Portanto, aumentando a intensidade de turbulência, a energia gerada é superestimada em moderadas velocidades do vento e subestimada em altas velocidades do vento. Enquanto isso, os coeficientes de cisalhamento do vento variaram entre 0 e 0.2 para altas velocidades. Além disso, coeficientes de cisalhamento com valores elevados, perto de 0.4, foram encontrados em baixas velocidades do vento. Este trabalho visou também comparar modelos de esteira turbulenta de PARK (Jensen), Frandsen, Larsen and Eddy Viscosity (Ainslie) com resultados obtidos pelo LiDAR, além disso foi realizado uma simulação numérica da esteira turbulenta utilizando Fluent CFD com as equações médias de Reynolds (RANS) que resolvem o modelos de duas equações diferenciais para obter a viscosidade turbulenta. A turbulência foi fechada pelo modelo ?????, sendo o modelo de esteira turbulenta desenvolvido para uma única turbina num terreno plano. O modelo de PARK obteve os melhores resultados para linha de centro longitudinal em relação as velocidades de 6 a 8 ms-1. Entretanto, para velocidade de 9 a 12 ms-1 , o modelo de EDDY VISCOSITY apresentou o melhor desempenho. As análises de seção transversal apresentaram o modelo de PARK como melhor resultado para 500 m. Enquanto isso, para 700 m de seção transversal, o melhor desempenho foi obtido pelo modelo de LARSEN. Palavras-chave: Energia Eólica, Modelo de Esteira Turbulenta, LiDAR, Análises do Vento.
Abstract: Wind power has gained significant share in the global power production. However, the wind power output efficiency is only about 30% of the wind kinetic energy. Because of that, it is essential to study the efficiency of these power generation systems by assessing the effects that wind parameters and wakes will have on the whole system. Hence, a complete assessment of wind resources is crucial to retain full advantage of wind power. This study aims to investigate the efficiency of wind energy generation in two North American Wind Farms, through wind data investigation and wake modeling. The data analyzed are the SCADA data and the data collected by LiDAR measurements. The wind data analysis has estimated parameters as wind shear, wind rose, wind speed profile and turbulence intensity. Therefore increasing turbulence intensity the power output is overestimated at moderate wind speeds and underestimated at higher wind speeds. Meanwhile, the wind shear coefficients were found to vary between 0 and 0.2 at higher inflow velocities. High wind shear values, close to 0.4, were recorded for lower inflow velocities. The goal of the wake models is to simulate the turbine induced wind speed deficits and the ratio of restoration to the free stream velocity. This work has compared the PARK (Jensen), Frandsen, Larsen and Eddy Viscosity (Ainslie) models with LiDAR wake measurements, besides that it has performed a numerical simulation of the wind turbine wake using the Fluent CFD with the Reynolds Averaged Navier Stokes (RANS) equations that solves two differential equation model to obtain turbulent viscosity. The turbulence was closed by the ????? model, where the wake modeling has been developed for a single turbine on a flat terrain. In terms of centerline wake analysis, the PARK wake model yielded the best velocity simulations for inflow winds from 6 to 8 ms-1. However, the EDDY VISCOSITY wake model yielded the best performance for wind speed bins from 9 to 12 ms-1. The cross section wake analysis presented for the 500 m cross section, the domination by the PARK model. Meanwhile, along the 700 m cross section, the LARSEN wake model produced the best simulations. Key-words: Wind Power, Wake Modeling, LiDAR, Wind Analysis.
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Paré, Jean-David. "Taming the wind." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp03/MQ31631.pdf.
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Sogand, Yousefbeigi. "Wind Farm Optimization." Master's thesis, METU, 2013. http://etd.lib.metu.edu.tr/upload/12615685/index.pdf.
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In this thesis, a mixed integer linear program is used to formulate the optimization process of a wind farm. As a start point, a grid was superimposed into the wind farm, in which grid points represent possible wind turbine locations. During the optimization process, proximity and wind interference between wind turbines were considered in order to found the power loss of the wind farm. Power loss was analyzed by using wind interference coefficient, which is a function of wind intensity interference factor (WIIF), weibull distribution and power of the wind turbines. Two different programsGenetic Algorithm and Lingo, were used to solve the MILP optimization formula and results were compared for different cases in the conclusion part.
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Mitchell, Andrew J. "Wind Turbine Noise." Thesis, University of Canterbury. Mechanical Engineering, 2004. http://hdl.handle.net/10092/6622.
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The objectives of this thesis were (i) to investigate the main sources and paths of noise on modern utility
size wind turbines; (ii) to explore methods of reducing the noise; (iii) to assess our current ability to
accurately predict and measure wind turbine noise. The accomplishment of these objectives would enable
quieter wind turbines to be developed and allow them to be located near residential dwellings with greater
confidence that the noise would not be a nuisance.
A comprehensive review of the current literature was carried out and the findings were used as a basis for
the investigative work conducted. It was found that wind turbine noise could be classed as either
aerodynamically produced noise or mechanically produced noise. Aerodynamically produced noise on
wind turbines arises mainly from the interaction of the flow over the blade with the surrounding air.
Mechanically produced noise arises from a number of sources such as the gearbox, generator and
hydraulic pumps. The noise can be radiated directly from the noisy component (airborne) and / or
transferred through the structure of the turbine and radiated elsewhere (structure-borne) such as the tower.
The prototype Windflow 500 wind turbine near to Christchurch was used for the majority of the
investigative work carried out, and to assess the predictions made. The main radiators of noise from the
turbine were identified as the blades (86 – 90% of the total sound power), the tower (initially 8 – 12% but
later reduced to ~4% of the total sound power), and the nacelle cladding (1% of the total sound power).
A prominent tone in the sound power spectrum from the turbine was observed in the 315 Hz 1/3 octave
band. This was shown to be predominantly caused by gear meshing in the second stage of the gearbox at
311 Hz. The presence of the tone was significant because under commonly used standards a tonal penalty
would be applied to the measured sound pressure level from the turbine to account for the extra
annoyance caused by the tone. This in turn would mean that any potential wind farms would need to be
sited further from residential dwellings than would otherwise be necessary in order to comply with noise
regulations. Investigations were carried out that addressed the noise radiated from each of the main contributors
outlined above. The sound power level radiated from the tower was found to be effectively reduced by
attaching rubber tiles at strategic locations inside the tower. Noise radiated from the nacelle was reduced
with a combination of acoustic insulation and acoustic absorption inside the nacelle. An investigation
into the gearbox noise was also carried out. Attempts to reduce the tonal noise caused by gear meshing
were made with little success but the investigation provided a good basis upon which to conduct further
work.
Preliminary investigations into both structure-borne and aerodynamically generated blade noise were
carried out. The structure-borne blade noise investigation showed that the blades readily vibrated at a
range of frequencies, the result being that structurally transmitted noise radiated from the blades was
likely to be present at high levels. Research showed that the structure-borne noise radiated from the
blades could be significantly reduced by partially filling the internal cavity of the blades with foam. The
investigation of aerodynamically produced noise was carried out on a section of Windflow 500 blade in
the low noise wind tunnel at the University of Canterbury. The tests showed that the blade generated
noise at a range of frequencies including those in the 315 Hz 1/3 octave band. This suggested that the
tonal noise measured from the blades was not only due to structurally transmitted noise from the gearbox
but was also contributed to by aerodynamically produced noise. It was found that the noise from the
blade section could be reduced by up to 4.5 dB at certain frequencies by attaching serrated strips to the
trailing edge of the aerofoil.
Empirical equations for prediction of wind turbine sound power levels were evaluated and found to be in
good agreement with measured data. It was found that accurate spectral predictions of the sound power
level were much more difficult. However given spectral data for a turbine, it was found that accurate
predictions of the noise propagation from the turbine could be made, taking into account meteorological
effects and the effect of complex topography. It was found that the CONCAWE propagation model was
well suited to the prediction of noise propagation from wind turbines because of its superior handling of
meteorological effects. In an investigation carried out which modelled the Gebbies Pass site of the Windflow 500 it was found that the CONCAWE model could predict sound pressure levels from the
turbine to within 2 dB at distances of up to 1400 m.
Further work in the area of wind turbine noise should be focused on the reduction of blade noise. This is
especially relevant to the Windflow 500 since blade noise was found to be by far the largest contributor to
total noise radiated from the turbine. Acoustic treatments elsewhere would therefore produce only small
reductions in the total sound power emitted by the turbine.
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Rahal, Zeina. "Wind powered desalination." Thesis, Loughborough University, 2001. https://dspace.lboro.ac.uk/2134/7466.
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This thesis investigates the technical problems associated with large-scale stand-alone wind powered desalination employing a short-term energy store, particularly the complexities associated with the intermittent operation of the desalination plant. To achieve this, a non-linear, time domain system model of an existing wind powered desalination plant has been developed using the propriety code Simulink. Two desalination techniques have been considered: reverse osmosis and electrodialysis, due firstly to their relatively low specific energy consumption, and secondly, their efficient coupling to a wind turbine generator. As a way of reducing power mismatch, optimising water production, and above all reducing the switching rates of the desalination units, operation of the reverse osmosis and electrodialysis units under variable power conditions is suggested. Little information is available on plant performance under such conditions. A mathematical model has therefore been developed to ascertain the performance of reverse osmosis and electrodialysis processes under transient power conditions. The model consists of the set of partial differential equations (PDEs) describing the conservation of mass, momentum and chemical species coupled with the appropriate boundary conditions. A numerical solution based on the finite volume method has been employed to solve for the system of PDEs, as no analytical solution is available for the particular set of model equations derived. Sensitivity of plant performance to key design parameters (such as operating pressure and energy storage capacity) and operational strategies is predicted from simulation results. This technology is economically attractive for islands where wind energy density is high and water resources are scarce.
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BALDVINSDÓTTIR, UNA. "The Wind Projects." Thesis, Högskolan i Borås, Institutionen Textilhögskolan, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:hb:diva-17401.
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The Wind Projects are based around ideas about materialization. They are an attempt at combining factors related to textiles, such as patterns, structure, materials and body with abstract ideas about movement, change, unpredictability and interrelated relationships between materials, environments objects and actions.Program: Master in Textile Design
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Kim, Sung Ho 1969. "Cartographing the wind." Thesis, Massachusetts Institute of Technology, 1998. http://hdl.handle.net/1721.1/67517.
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Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Architecture, 1998.Most ill. printed on mylar transparencies.
Includes bibliographical references (leaf 41).
At the beginning of the design process the architect possesses only a random collection of information, requirements, intentions, and assumptions, and then suddenly on the drawing board appears a proposal for an architectural form. How is th is idea generated, what influences its shape, from what is it derived from? Faced with the daunting task of conceiving a building form, should one first study the functional requirements, or manipulate geometrical systems, or give expression to inner intuitions? During this critical stage of creating something out of nothing, architects desire a set of normative principles that could guide their activities. Many theories about the source of form were developed to help govern architectural practice, and much practice derived from these theories. This question about the source of form is equally central to theories in other fields from art and architectural history to anthropology. However these other fields are not concerned with creating architectu ral forms, but are attempts to explain the social, cultural, and historical phenomena which are manifested in the built environment. Today we must acknowledge that any new form of architecture not only has to rethink the specific forms it produces, but, as a condition for doing so, has to rethink the form, shape, and articulation of its practice of architecture. Henri FociII on suggests that all of life, has a certain shape, a certain form that is the result of its affiliations and intermingling with other forms. It is in the shaping of the form of practices including techniques, investigations, operations, perceptions, and logics, that the new architectural form prevail. Cartographing the wind is a research into an invention of new architectural practice. By experimenting and developing the analysis\ design of an enveloping architecture capable of reconfiguring and mapping aerodynamic spectrum around the object. Sophisticated configuration of programs emerge to respond with complex order to determine and redefine the new limits of our condition of architectural experience. Like a net, a map does not simply describe what is. A map does not only set up a grid which determines what can be found by selection or omission. Nor is it merely a series of lines inscribed on a blank surface. There is an alterity which provokes the desire to map, to contain and to represent which is to say, to embody or to embrace the unknown. Cartographing the Wind focuses on the shift from the fixed static notions of architecture to dynamiC formations. The mapping of the nonlinear dynamics in wind forces transforms and destabilizes classical perceptions of space, geometry, program, and universality.
by Sung Ho Kim.
M.S.
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Золотова, Світлана Григорівна, Светлана Григорьевна Золотова, Svitlana Hryhorivna Zolotova, and I. A. Papus. "Electricity from wind." Thesis, Видавництво СумДУ, 2011. http://essuir.sumdu.edu.ua/handle/123456789/13438.
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Золотова, Світлана Григорівна, Светлана Григорьевна Золотова, Svitlana Hryhorivna Zolotova, and O. V. Leunova. "Wind Energy Sources." Thesis, Видавництво СумДУ, 2011. http://essuir.sumdu.edu.ua/handle/123456789/13443.
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Ross, Ian J. "Wind tunnel blockage corrections : an application to vertical-axis wind turbines /." Dayton, Ohio : University of Dayton, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1271306622.
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Thesis (M.S. in Aerospace Engineering) -- University of Dayton.Title from PDF t.p. (viewed 06/22/10). Advisor: Aaron Altman. Includes bibliographical references (p. 101-104). Available online via the OhioLINK ETD Center.
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Kayisoglu, Bengi. "Investigation Of Wind Effects On Tall Buildings Through Wind Tunnel Testing." Master's thesis, METU, 2011. http://etd.lib.metu.edu.tr/upload/12613324/index.pdf.
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In recent years, especially in the crowded city-centers where land prizes have become extremely high, tall buildings with more than 30 floors have started to be designed and constructed in Turkey. On the other hand, the technical improvements have provided the opportunity of design and construction of more slender structures which are influenced by the wind actions more. If the building is flexible, wind can interact with it so the wind induced oscillations can be significantly magnified. In order to analyze the response of such buildings under wind effects, wind tunnel tests are accepted to be the most powerful tool all over the world. In this study, a series of tests were performed in Ankara Wind Tunnel on a model building in the shape of a rectangular prism. For the similitude of flow conditions, passive devices were designed. The response of the model building was measured through a high frequency base balance which was designed specifically for this case study. Through the tests, the effects of turbulence intensity, vortex shedding and wind angle of attack on the response of the building were questioned. Finally, the results were compared with the results of various technical specifications about wind.
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Klain, Sarah Catherine. "Wind of change : offshore wind farms, contested values and ecosystem services." Thesis, University of British Columbia, 2016. http://hdl.handle.net/2429/59560.
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Increasing reliance on renewable energy promises to reduce carbon emissions. Although national-scale polls demonstrate high levels of public support for developing renewable energy, local opposition has led to cancelations of renewable energy projects globally. This dissertation empirically investigates barriers to the siting of offshore wind farms in reference to their perceived risks and benefits; people’s willingness to pay to mitigate environmental risks; values that influence these choices and attitudes; and public engagement processes used to engage local citizens in decisions about siting and energy options. The first study investigates perceptions of offshore wind farm impacts and why risks to some ecosystem services (benefits from nature to people) may induce greater concern than others. These differences are attributed to the affective ways in which people perceive risk. Affectively-loaded impacts (e.g., harm to charismatic wildlife, visual intrusion) were assigned greater weight than more easily quantifiable impacts (e.g., displacement of fishing, impact to tourism). This study suggests that government authorities and developers can anticipate and more explicitly address affective dimensions of renewable energy proposals. The second study quantifies stated preferences for specific attributes of wind farms: effect on marine life, type of ownership, distance from shore, and cost. The strongest preference was for farms that greatly increased biodiversity via artificial reefs at an additional cost of $34-42/month. This demonstrates statistically significant willingness to pay for ecologically regenerative renewable energy development. The third study pilots methods on ‘relational values,’ which link people to ecosystems and include associated principles, notions of a good life and virtues. Results suggest relational values are distinct from standard measures of ecological worldview (New Ecological Paradigm) and predictive of attitudes towards offshore wind farms. The fourth study assesses attributes of effective public engagement processes to site renewable energy projects near three island communities. Amongst the array of criteria for robust analytic deliberative processes, good public engagement may be condensable to two themes: enabling bidirectional deliberative learning and providing community benefits. Attending to these themes may improve relationships among communities, government authorities and developers when deciding if and where to site renewable energy infrastructure.Science, Faculty of
Resources, Environment and Sustainability (IRES), Institute for
Graduate
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Halliday, J. A. "Wind meteorology and the integration of electricity generated by wind turbines." Thesis, University of Strathclyde, 1988. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=21325.
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The generation of electricity using wind turbines is now widespread and commercially viable. There are two aspects of wind energy which are critically important. Firstly, the evaluation of the wind resource, both on nationally and on a local scale. Secondly, the integration of electricity generated by wind turbines into existing electricity grids without reducing the reliability of supply or reducing the overall economic efficiency of the system. This thesis examines both these aspects. Chapters 3 and 4 are concerned with the large scale utilisation of wind energy. Chapter 3 discusses the suitability for wind energy evaluation of the data held by the UK Meteorological office, describes the results of a detailed examination of over 130 station-years of hourly data, and recommends areas of further study as well as a UK standard for site description. Chapter 4 describes a computer model used to examine the effects of integrating wind-generated electricity into the CEGB National Grid and the results obtained with it. The relative importance of dispersal of wind turbines, load and wind forecasting, variation of turbine characteristics and inter-annual variability of wind speed is determined. Chapters 5 and 6 are concerned with a detailed evaluation of thewind energy potential on the Shetland island group. Chapter 5 describes the planning, testing and installation of two hill-top monitoring stations on Shetland and the results found. Chapter 6 describes the development of a computer model of the Shetland Power Station, which is used to examine how the introduction of wind turbines would affect the operation of the power station and the maximum energy penetration possible before power cuts occur. Both chapters conclude with detailed recommendations which will be of worldwide use as the wind energy potential of other diesel-fuelled grids is determined.
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Barthelmie, Rebecca. "Predicting on- and off-shore wind speeds for wind energy applications." Thesis, University of East Anglia, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.364335.
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Al-Qahtani, Turki Haif. "An improved design of wind towers for wind induced natural ventilation." Thesis, University of Bath, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.323566.
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Kalmikov, Alexander G. "Modeling wind forcing in phase resolving simulation of nonlinear wind waves." Thesis, Massachusetts Institute of Technology, 2010. http://hdl.handle.net/1721.1/57791.
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Thesis (S.M.)--Joint Program in Oceanography/Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Dept. of Mechanical Engineering; and the Woods Hole Oceanographic Institution), 2010.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 148-152).
Wind waves in the ocean are a product of complex interaction of turbulent air flow with gravity driven water surface. The coupling is strong and the waves are non-stationary, irregular and highly nonlinear, which restricts the ability of traditional phase averaged models to simulate their complex dynamics. We develop a novel phase resolving model for direct simulation of nonlinear broadband wind waves based on the High Order Spectral (HOS) method (Dommermuth and Yue 1987). The original HOS method, which is a nonlinear pseudo-spectral numerical technique for phase resolving simulation of free regular waves, is extended to simulation of wind forced irregular broadband wave fields. Wind forcing is modeled phenomenologically in a linearized framework of weakly interacting spectral components of the wave field. The mechanism of wind forcing is assumed to be primarily form drag acting on the surface through wave-induced distribution of normal stress. The mechanism is parameterized in terms of wave age and its magnitude is adjusted by the observed growth rates. Linear formulation of the forcing is adopted and applied directly to the nonlinear evolution equations. Development of realistic nonlinear wind wave simulation with HOS method required its extension to broadband irregular wave fields. Another challenge was application of the conservative HOS technique to the intermittent non-conservative dynamics of wind waves. These challenges encountered the fundamental limitations of the original method. Apparent deterioration of wind forced simulations and their inevitable crash raised concerns regarding the validity of the proposed modeling approach. The major question involved application of the original HOS low-pass filtering technique to account for the effect of wave breaking. It was found that growing wind waves break more frequently and violently than free waves.
(cont.) Stronger filtering was required for stabilization of wind wave simulations for duration on the time scale of observed ocean evolution. Successful simulations were produced only after significant sacrifice of resolution bandwidth. Despite the difficulties our modeling approach appears to suffice for reproduction of the essential physics of nonlinear wind waves. Phase resolving simulations are shown to capture both - the characteristic irregularity and the observed similarity that emerges from the chaotic motions. Energy growth and frequency downshift satisfy duration limited evolution parameterizations and asymptote Toba similarity law. Our simulations resolve the detailed kinematics and the nonlinear energetics of swell, windsea and their fast transition under wind forcing. We explain the difference between measurements of initial growth driven by a linear instability mechanism and the balanced nonlinear growth. The simulations validate Toba hypothesis of wind-wave nonlinear quasi-equilibrium and confirm its function as a universal bound on combined windsea and swell evolution under steady wind.
by Alexander G. Kalmikov.
S.M.
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Nanopoulos, Andrew. "Valuation of wind energy projects and statistical analysis of wind power." Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/74932.
Full textAbstract:
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2012.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 221-225).
As energy becomes an increasingly important issue for generations to come, it is crucial to develop tools for valuing and understanding energy projects from an economic perspective since ultimately only economically viable solutions will be pushed forward. A model is developed for valuing a generic offshore floating wind farm from a corporate finance perspective. The model is used to value the project based on multiple valuation metrics and to generate sensitivity analyses on multiple important technical, cost and financial parameters. It is found that offshore wind projects can be economically viable under current conditions contingent on high annual mean wind speed and government support. In addition, it is also found that financial parameters prove to be equally or even more important than technical parameters in affecting the overall project value. Furthermore, the wind speed and power output are modeled using a mean reverting Ornstein - Uhlenbeck process whereby it is found that while wind speed is positively autocorrelated, the averaging period plays an important role in determining the nature and extent of the autocorrelation. Finally, the valuation is extended and generalized to a Black-Scholes option based valuation of any project whose underlying asset follows a mean reverting process, whereby a model is developed to find the debt and equity values under the assumption of time independence. The tools developed for this purpose can prove to be useful in other applications besides energy, such as shipping and commodities, as the underlying characteristics of energy projects are often similar across other markets.
by Andrew Nanopoulos.
S.M.