Wind Engineering

Wind energy is one among the most promising renewable energy sources, and hence there is fast growth of wind energy farm implantation over the last decade, which is expected to be even faster in the coming years. Wind turbine blades are complex structures considering the different scientific fields involved in their study. Indeed, the study of blade performance involves fluid mechanics (aerodynamic study), solids mechanics (the nature of materials, the type of solicitations …), and the fluid coupling structure (IFS). The scope of the present work is to investigate the mechanical performances and structural integrity of a large offshore wind turbine blade under critical loads using blade element momentum. The resulting pressure was applied to the blade by the use of a user subroutine “DLOAD” implemented in ABAQUS finite element analysis software. The main objective is to identify and predict the zones which are sensitive to damage and failure as well as to evaluate the potential of c...

This report presents the work I did as part of my graduation project. It consists of designing, studying and dimensioning the JW Marriott Tower in Casablanca Marina.
Being one of the largest cities in Africa, Casablanca plans to develop its international character by enriching its heritage of skyscrapers which are the symbol of power, energy and splendour of cities.
Having a unique architecture for the first time in Morocco, the tower presents enormous difficulties in terms of design and study since they work on the limits of current standards and regulations.
In this project I present initially a dossier about towers, their construction systems and their most used materials. Subsequently I explain the final design I have developed in accordance with the architectural plans and then I present the geotechnical context of the area and define the general hypothesis.
In the study and dimensioning phase, I study the structure in two approaches: a static approach and a dynamic approach. The static approach consists in studying the static behaviour of the tower vis-a-vis the permanent the exploitation loadings before dimensioning the structural elements outside the bracing system. In the dynamic approach I study the different horizontal and vibratory stresses, starting with the wind and then the seismic calculation.
After determining these stresses, I study the seismic design of the plates and shells as well as the foundations and the retaining walls and their stabilities and justifications in accordance to the ultimate, service and accidental states.

Vent holes can be used to reduce the aerodynamic pressure loads on nonstructural elements of buildings. The analysis of these loads applied on nonstructural elements of buildings (window panes, closure panels, etc.) with vent holes, under gusty wind conditions, have been studied both experimentally and employing a theoretical model. An experimental setup based on an open circuit, closed test section, and low speed wind tunnel, designed and built at the Instituto de Microgravedad “Ignacio Da Riva” of the Universidad Politécnica de Madrid (IDR/UPM) has been used. A mechanism in the wind tunnel generates sinusoidal gusty winds inside the test section. Theoretical predictions of the pressure loads have been obtained using a mathematical model based on the mass conservation equation and polytropic law gas evolution. In the experimental setup, an air reservoir with a vent hole has been selected as a model to simulate the internal pressure loads acting on the walls of a building under a ta...

A state-of-art wind mapping system, the Wind Energy Simulation Toolkit (WEST), was developed in the Meteorological Service of Canada (MSC) for use by the wind energy industry. WEST is based on a statistical-dynamical downscaling approach, i.e. (i) a statistical analysis of climate data to determine the basic atmospheric states, and (ii) a dynamic adaptation of each basic state to high-resolution terrain and surface roughness by using mesoscale and microscale models. The approach has already been used by Frank and Landberg (1997), in their KAMM/WAsP method, to create a numerical wind atlas. The novel part of WEST is the fixed wind-speed interval in classification scheme and the integration of different modules (meso-/micro-scale models and statistical module) into a single toolkit in a more portable form. WEST was built for use by industries not having sophisticated computer facilities. WEST is applied to the Gaspé region of Canada. The mesoscale model MC2 (operated within WEST) is r...

This work demonstrates a technique to identify information about the ice mass accumulation on wind turbine blades using its natural frequencies, and these frequencies reduce differently depending on the spatial distribution of ice mass along the blade length. An explicit relation to the natural frequencies of a 1-kW wind turbine blade is defined in terms of the location and quantity of ice mass using experimental modal analyses. An artificial neural network model is trained with a data set (natural frequencies and ice masses) generated using that explicit relation. After training, this artificial neural network model is given an input of natural frequencies of the iced blade (identified from experimental modal analysis) corresponding to 18 test cases, and it identified ice masses’ location and quantity with a weighted average percentage error value of 17.53%. The proposed technique is also demonstrated on the NREL 5-MW wind turbine blade data.

In this paper, the objective of this study is to evaluate the wind potential of the site Sidi Daoud, at 30m height above ground level, by three statistical methods (meteorological, Weibull and Rayleigh), to identify the characteristic parameters of aerogenerator AE-32 and to determine its energetic efficiency on site. Index Terms-Tunisia, Wind farm of Sidi Daoud, Wind energy, Meteorological distribution, Weibull method, Rayleigh method, Aerogenerator AE-32, mean efficiency. 1. NOMENCLATURE V Wind speed (m/s) F(V) Cumulated frequency f(V) Occurrence frequency n Number of wind speed classes Vm Mean speed (m/s) Vf Most frequent speed (m/s) Ve Most energetic speed (m/s) Pd Power density at Betz limit (W/m²) Ed Available energy at Betz limit (kWh/m²/year) Eu Usable energy (kWh/m²/year) Er Recoverable energy (kWh/m²/year) Ps Electric power on the aerogenerator outlet (kW). ηd Mean efficiency relating to the available energy ηu Mean efficiency relating to the usable energy η Global mean efficiency ηm Gearbox efficiency (96%) ηg Generator efficiency (96.2%) Cp Power coefficient λ Specific speed N Rotational speed of rotor (tr/mn) A Weibull scale factor (m/s) K Weibull shape factor ρ Air density (1.225 kg/m 3) σ(M,W,R) Standard deviation calculated from the meteorological, Weibull and Rayleigh methods (m/s)

Wind characteristics and wind turbines characteristics in Sidi Daoud site, Tunisia, have been thoughtfully analyzed based on a measured data source during the year 2004 at heights of 45, 50 and 60m above ground in two places (Mast 1 and Mast 2). The yearly wind speed distribution and wind power density are evaluated to provide annual estimation of wind energy potential. A mathematical formulation using a one-parameter Rayleigh wind speed distribution is established to estimate the wind energy generated by an ideal turbine and the yearly actual wind energy generated by wind turbine operated at Boltzman relation of power between cut-in and cutout wind speed. Three characteristic parameters of wind turbine (the wind turbine efficiency, the use factor and the availability rate) are investigated and compared for three real wind turbines installed in site (MADE AE-45, AE-52 and AE-61). The identification of the wind shear coefficient in two places of the site has enabled us to study the vertical variability of wind. Using the power law, an extrapolation study of the obtained results with height is also carried out. The results show the general availability of wind energy potential across Sidi Daoud site.

Since ancient times, Architecture have always been an environment sensitive field in their design approach which makes it deal with various obstacles present in the nature. The study of local climatic characteristics navigates the building design to a great extent which makes Architecture defining its own styles from one place to other. The hand in hand coordination of design with engineering has helped world witnessing the revolution in building cities across the globe. The approach has also changed from battle to cooperative over a period of time that makes it a more cohesive setting. With the advent of mega structures even engineering and technology are also discovering new horizons of their domain by bringing the reality to the creative ideas of Architects. Wind has been the most important aspects that needs attention while making new age structures of mega million projects reaching sky. The paper discusses various ways the wind and Architecture can together accommodate through ...

Este trabalho apresenta por meio de revisão bibliográfica as
vantagens e desvantagens das redes centralizadas e descentralizadas de distribuição de energia eólica, principalmente no que se refere aos aspectos socioeconômicos, ambientais e tecnológicos.

Le but de ce papier est de constituer une base de données aux utilisateurs de l'énergie éolienne en Tunisie. Il présente l' étude de dix-sept sites synoptiques distribués sur tout le territoire tunisien. A partir des données météorologiques fournies par l' Institut National de la Météorologie (I.N.M.), nous avons évalué les caractéristiques de la vitesse du vent et l'énergie éolienne disponible à une hauteur de 10 m au-dessus du sol et en rase campagne par deux méthodes statistiques : Météorologique et Weibull. Une étude d'extrapolation de ces caractéristiques en fonction de la hauteur est présentée. Les résultats obtenus donnent une vision globale de la distribution du potentiel du vent et définissent les zones les plus ventées en Tunisie. Mots clés: Tunisie, Vitesse de vent, Energie éolienne, Méthode météorologique, Méthode de Weibull, Rose du vent. Abstract: The goal of this paper is to constitute a database to the users of the wind energy in Tunisia. It presents the study of seventeen synoptic sites distributed on all the Tunisian territory. From the meteorological data provided by the Meteorology National Institute (I.N.M.), we have evaluated the wind speed characteristics and the wind energy available to a 10 m height above the ground and in open area by two statistical methods: meteorological and Weibull. A study of extrapolation of these characteristics in relation to the height is presented. The results obtained give a global vision of the wind energy distribution and define the windiest zones in Tunisia.

The purpose of this paper is to constitute a database for the users of the wind power. It presents the study of 17 synoptic sites distributed on all the territory of Tunisia. From the meteorological data provided by the Meteorology National Institute (INM), two statistical methods (meteorological and Weibull) are presented to evaluate the wind speed characteristics and the wind power potential at a height of 10 m above ground level and in an open area. An extrapolation of these characteristics with the height is also carried out. The results obtained give a global vision of the distribution of the wind potential in Tunisia and define the most windy zones. r

Commercial production greenhouses are widely used to produce plants and crops. From the structural engineering viewpoint, among the loads that act on greenhouses, wind and snow loads are the major ones. This paper focuses on the former, particularly on wind pressure coefficients. Design and construction of greenhouses should consider wind loads in order to ensure seamless operation, overall stability, durability, and safety, even though human occupancy is limited. Classification and design of greenhouses is typically based on European standards, which cover a variety of geometries and conditions. Some recent research studies suggest, however, that greenhouse design standards should be revised to ensure structural safety of greenhouses subject to strong wind loads. Triggered by this recent outcomes, this paper reviews existing literature on the topic: (a) briefly presenting the state of the art methods for determining wind pressures on greenhouses; (b) comparing the EN 13031-1 pressu...

Nigeria is ranked among the lowest countries in terms of per capita energy consumption in the world. It also produces significant CO2 emissions. Hence, there is a vital need for clean and accessible energy in the country. Wind energy systems are one of such options. In this work, wind speed data measured at 10m above ground level from 2011 to 2016 for thirteen Nigerian sites are analyzed and the two-parameter Weibull distribution probability density function is used for wind power assessment. Moreover, the average wind power density and the corresponding wind energy density are obtained and the potential of electricity generation by means of wind turbines is assessed. The results reveal that Kano and Jos have the highest wind power potential with wind power densities of 79.96 W/m 2 and 133 W/m 2 , respectively. With about 43 and 20 MWh of annual generated electric energy at Jos and Kano, respectively, these two sites proved to be the most promising candidates for utilizing wind turbines for electricity generation.

Este artículo presenta un modelo estocástico para la simulación del comportamiento de la velocidad del viento en dirección horizontal. Además, se desarrollan modelos tanto para grandes como pequeñas escalas de tiempo. Estos modelos se obtienen a partir de una investigación documental en la literatura especializada. En el modelo a pequeñas escalas de tiempo se consideran cuatro componentes: promedio, rama, ráfaga, y turbulencia. El comportamiento de la componente turbulencia en la velocidad del viento fue modelado incluyendo una variable aleatoria. También se muestra el modelo para grandes escalas de tiempo, a partir de ciertas consideraciones para el modelo de pequeñas escalas de tiempo. Se presenta una discusión sobre la intensidad de la turbulencia y la longitud de escala de los fenómenos. Finalmente, el modelo fue validado mediante simulación en Matlab de un caso bien documentado.

Wind damage to asphalt shingles is usually obvious.  However, there remain a number of issues such as cupping, splitting, and lack of bonding which some people falsely attribute to wind.  This paper discusses what wind damage is and is not to asphalt shingles.  The paper also discusses what intentional damage looks like when persons try to simulate wind damage.

In wind load calculations based on pressure measurements, the concept of 'tributary area' is usually used. The literature has less guidance for a systematic computational methodology for calculating tributary areas, in general, and for scattered pressure taps, in particular. To the best of the author's knowledge, there is no generic mathematical equation that helps calculate the tributary areas for irregular pressure taps. Traditionally, the drawing of tributary boundaries for scattered and intensively distributed taps may not be feasible (a time and resource consuming task). To alleviate this problem, this paper presents a proposed numerical approach for tributary area calculations on rectangular surfaces. The approach makes use of the available coordinates of the pressure taps and the dimensions of the surface. The proposed technique is illustrated by two application examples: first, quasi-regularly distributed pressure taps, and second, taps that have scattered distribution on a rectangular surface. The accuracy and the efficacy of the approach are assessed, and a comparison with a traditional method is presented.

Edificações em geral estão submetidas a carregamentos de vento, que variam de acordo com alguns fatores de exposição. Tais fatores devem ser considerados na fase de projetos, para alcançar bons níveis de segurança e confiabilidade estrutural. A ação do vento começou a ser um aspecto preocupante, após a implementação de construções altas e o colapso na ponte de Tacoma Narrows. Na atualidade, a aplicabilidade técnica das recomendações normativas de vento, são mensuradas através da NBR 6123 (1988), no entanto, as considerações da norma remontam a época de limitações tecnológicas, deixando de considerar os avanços feitos nas últimas décadas. O túnel de vento é considerado o recurso mais eficaz na determinação de esforços nas edificações, sendo um meio balizador para a verificação da norma. Neste trabalho, será apresentado um breve estudo sobre pesquisas que, com o avanço da tecnologia, demostram diferenças nos valores de pressões devido ao vento, proposto pela NBR 6123 (1988). Foram estudados 5 relatos de casos na literatura, que abordam sobre esforços devido ao vento ensaiados em túnel de vento, por conseguinte, comparou-se estes esforços, com os encontrados pela norma, para encontrar uma diferença percentual entre métodos. Esta técnica investigou em muitas situações, grandes diferenças entre os métodos propostos, em alguns casos o valor obtido pela NBR chegou a 29% em relação ao túnel de vento. Uma análise comparativa foi realizada entre os intervalos máximos dos valores da relação NBR/Túnel, entre os relatos estudados, onde pode observar que ora a norma está a favor a favor da segurança, ora a favor da economia. Após as análises, é possível afirmar que alguns tópicos da NBR 6123 (1988) requerem revisão, para que diminua esta diferença entre métodos, e a norma tenha valores mais precisos.

This interactive qualifying project focused on the ever advancing hybrid vehicle technology and
its integration with wind energy. The main objective of this project is to design and fabricated a self-starting
small vertical axis wind Turbine (VAWT) .This VAWT s can be mounted over the roof of the car or in front of
the cooler. Usually, a car moves through a layer of fluid and this fluid layer always is a disadvantage for
the moving car because it poses a drag force due to moving forward . In this research project, we are going
to use this force for developing electrical energy. This VAWT is build to achieve RPM at minimum wind
speed. The Twisted blade is the main function which plays the role to rotate it at minimum wind speed. Our
optimized view for this project is to set this VAWT in a car and run it by wind. From experiment 11.77watt
power can be generated when the turbine is run at 112rpm for the wind speed is 6m/s.

A series of wind tunnel tests were performed to investigate the effect of turbulent inflows on the aerodynamic characteristics of variously modified leading-edge protuberanced (LEP) wing configurations at various turbulence intensities. A self-developed passive grid made of parallel arrays of round bars was placed at different locations of the wind tunnel to generate desired turbulence intensity. The aerodynamic forces acting over the baseline straight leading-edge model and the modified small, medium and high LEP wing configurations were obtained from the surface pressure measurements made over the wing at different turbulence intensities using MPS4264 Scanivalve simultaneous pressure scanner corresponding to a sampling frequency of 700Hz. All the test models were tested for a wide range of angles of attack ranging between À45 α 45 at turbulence intensities varying between 0.51% TI 4.92%. Results reveal that the time-averaged mean coefficient of lift (C L) increases with the increase in the turbulence intensity associated with smooth stall characteristics rendering the modified LEP test models advantageous. Furthermore, based on the surface pressure coefficients the underlying dynamics behind the stall delay tendency were discussed. Additionally, attempts were made to statistically quantify the aerodynamic forces using standard deviation at both the pre-stall and the post-stall angles.

Gastautor Naturwissenschaftler Prof. Dr. Klaus-Dieter Döhler
Seite 1
Erneuerbare Energie der Heizeffekt ist seit 40 Jahren bekannt
Solaranlagen heizen die Atmosphäre auf
ab Seite 9
Klima Atmosphärische Verwirbelung durch Turbinenblätter
Windkraftanlagen fördern Dürre
ab Seite 16
Keine „Globale Erwärmung“ auf dem Land
Umweltzerstörung durch Städte- und Straßenbau
Erderwärmung als systematischer Messfehler der Verstädterung
ab Seite 28
Anmerkungen vom Botschafter der physisch, lebendigen Erde zu
Energien und Haushalten mit Energien.
Die physisch, lebendige Erde schenkt jeden von uns täglich 129600 Energieeinheiten.
Je nach dem, wie Du aufmerksamer Leser und jeder andere Nicht-Leser auch, mit den täglich geschenkten 5 x 25920 = 129600 Energieeinheiten in deinen energetischen Wandlungsprozesen durch deine Teilhabe am Leben haushalten, oder wirtschaften tust, machst Du dich lieber Leser, so wie jeder andere Nicht-Leser auch,
- beim mehr benutzen an geschenkter Energieeinheiten  zu einen Mit-Täter am Leben minimierender energetischer Wandlungsprozesse.
- bei optimaler Ausnutzung der geschenkten Energieeinheiten bist Du ein Heiler - in der Balance - energetische Prozesse am Leben zu regenerieren und nicht mehr Energie zu gebrauchen als dir geschenkt wird.
- schaffst Du es, aus den geschenkten Energieeinheit neue Energien zu kreieren und an andere ab-, oder weiterzugeben, dann sei Dir gesagt:
Bist Du ein wunderbare Leser, ein Mit-Schöpfer am Leben energetischer Eandlungsprozesse.
Was die Energieeinheiten sind wird im Text Preis gegeben.

Outline
Introduction
•About the windmill
o Different components: Foundation and tower, Nacelle, Rotor, Blades
•Importance of tower in the wind turbine
o 20-25% of windmill cost is the tower
o Relation of tower height and energy output
•Types of turbines and relation to tower design
o Up-wind/Down-wind turbines
•Historical development of the tower
o From mill-houses to modern windmills
•Review of International and Canadian codes for tower design
o IEC(International Electro-technical Commission) 61400
o Ontario Building Code

Procedures for Design of Wind Towers
•Loads considered for design of wind towers
o Deterministic component
o Stochastic component
•Finite Element Analysis
•Computational Fluid Dynamics
•Dynamics
o Tower coupling
     Rotor Blade movement may either amplify or dampen tower oscillation
o Eigen Frequency: Frequency at which tower oscillates. And factors on which it depends:
     Thickness of walls
     Height
     Type of material
     Weight of Nacelle and Rotor
o Tower’s first natural frequency and classification of tower
     Soft-soft tower
     Soft Tower
     Stiff tower

Analysis and comparison of conventional and alternative tower designs/materials
Based on the section above, using the design factors, compare newer technologies like those given below to the conventional steel tube design used now.
• Steel tube ‘soft’ tower
• Steel multi-petal tower
• Steel space frame tower
• Concrete Towers
• Hybrid Towers

Conclusions and Recommendations
• Based on the analysis of different materials and designs, make observations regarding advantages and disadvantages of each alternative
• Conclude on the future path the tower design is taking and remark on the best alternative based on the factors considered in this report

This paper deals with an experimental and numerical dynamic characterization of two steel wind turbines currently located in Italy. The considered steel turbines are onshore and were originally built more than 20 years ago with 65 meters of height (from the ground level to the hub). Five years ago, they were unmounted and reassembled in the present location. During this phase, due to local and national environmental prescriptions, they were shortened to about 45 meters (hub height). Unfortunately, this procedure generated a huge problem in their structural behaviour: the fundamental frequency of vibration of both the "shorter" steel turbines become close to the working frequency of their rotors, causing a resonance problem. To evaluate exactly the turbine frequencies and modal shapes, structural monitoring involving several accelerometers has been implemented. Then, numerical finite element models (FEM) have been developed to investigate the influence of the soil-structure interaction (SSI) on the dynamic behaviour of these structures. Finally, two practical solutions to overcome the resonance problem are proposed and discussed. Since the investigated problems can arise for any worldwide wind turbine, the proposed solutions are of general validity and can be extended to many other different cases.

 Abstract-For solving the world energy crisis and environmental issues, great attention all over the world is paid towards the use of renewable energy sources. Special interest is paid towards wind energy because of it's competitively. Presently, Small Vertical Axis Wind Turbines (SVAWT) replaces horizontal axis wind turbines (HAWT), due to their self-starting, multi-directional, no yaw mechanism requirement for continuous orient towards the wind direction. Savonius wind turbines are executable in low wind speed regimes and which can be fitted on rooftops and also suitable for the urban areas. Blade aerodynamics in VAWT has significant effect on turbine efficiency. The present work, deals with the hybrid system, i.e. combination of two Vertical Axis Wind Turbine (VAWT), viz. Savonius and Giromill type of turbines. In the present work different geometries of Savonius wind turbine are experimentally studied in order to determine the most effective performance parameters. In the present work wind turbine blade are designed as per Savonius VAWT and arms as per Giromill Wind Turbine. For the turbine blade we have tested standard PVC pipes which are available in the market. We have performed wind tunnel test on three different PVC pipes having different diameters of 3", 4", and 6". The results show that 6" diameter PVC pipe is efficient among three. Eventually, we used dynamo for the production of electrical energy.

Increase of energy consumption in the world and importance of CO2 reduction
stimulate development of alternative sources of energy. Kazakhstan territory has high
potential for wind energy industry development. As a result, Republic of Kazakhstan
increases energy production from wind, solar and other renewable resources.
This purpose of the Project is Feasibility Report for construction of 50 MW wind farm
station near Ereymentau, Akomla region. Initially, current wind industry situation is
investigated in Chapter 1. After that, Ereymentau’ wind potential assessment is done in order
to calculate possible energy production. Then, turbine type is chosen and technical details of
wind park is analyzed. Afterward, detailed economy analysis of the project is given in
Chapter 6. Safety and Risk assessment are covered in Chapters 7 and 8. Next, environmental
impact is discussed in Chapter 9. Project Management is given in the last Chapter.
Summary of Final Feasibility of the wind park Project near Ereymentau and
recommendations are given in Chapter 11.

RESUME Cette communication présente une étude des caractéristiques de la vitesse du vent en fonction de la hauteur et leur effet sur la rentabilité énergétique des aérogénérateurs de la centrale éolienne de Sidi Daoud, Tunisie. Une étude d'extrapolation verticale à l'aide de la loi de puissance a permis de connaître l'évolution de la vitesse du vent à des altitudes représentant un intérêt énergétique.

I prepared this 47 page report in partial fulfilment of the requirements for admission into the corporate membership of the Nigerian Society of Engineers and towards the goal of registration with Council for the Regulation of Engineering in Nigeria. Corporate membership of the Nigerian Society of Engineers is only attained after passing a series of thorough assessment including but not limited to an oral interview, a written examination and submission of a technical report. The report contains two volumes: Volume I which details my postgraduate experience; and Volume II which gives the details of the design and construction of a hot air balloon which I undertook between 2013-2014.

ABSTRACT
This article aims to inform what kind of instrumentation and control must be in a wind power generating plant. It has a structure which twelve pages were made with the relationship at work and investigation of this type of industry. In the first pages you can find the parameters and activities that should be considered and appropriate instrumentation to perform different activities, intermediate pages are beginning to address the issue of control that best suits the system wind power generation
Keywords: Onshore, TLC, TCM, instrumentation, turbine, turbine, Tip Speed Ratio (TSR), power coefficient (Cp), anemometer, Instruments, energy generation.

Commercial production greenhouses are widely used to produce plants and crops. From the structural engineering viewpoint, among the loads that act on greenhouses, wind and snow loads are the major ones. This paper focuses on the former, particularly on wind pressure coefficients. Design and construction of greenhouses should consider wind loads in order to ensure seamless operation, overall stability, durability, and safety, even though human occupancy is limited. Classification and design of greenhouses is typically based on European standards, which cover a variety of geometries and conditions. Some recent research studies suggest, however, that greenhouse design standards should be revised to ensure structural safety of greenhouses subject to strong wind loads. Triggered by this recent outcomes, this paper reviews existing literature on the topic: (a) briefly presenting the state of the art methods for determining wind pressures on greenhouses; (b) comparing the EN 13031-1 pressure coefficients with those stemming from recent experimental studies on single-span pitched and arched roof greenhouses in South Korea; and (c) summarizing most recent comparative results for multi-span greenhouses. It concludes that these recent research studies are not enough to justify revision of EN 13031-1, and more measurement data and experimental or numerical studies are necessary to justify such a conclusion.

This qualitative research deals with moderation of vertical-axis wind turbine (VAWT) of Darrieus type. We performed a research in which three twisted bladed vertical axis wind turbines (VAWT) were designed and tested for optimal performance at various wind speeds. A blade with twist will have a variation in angle of attack from hub to tip because of the variation of distance from the hub. The lift and drag have optimum values for a single angle of attack so a blade without twist is less efficient than a blade with the proper twist to maintain a nearly constant angle of attack from hub to tip. Even the blades were twisted and the pitch angle will change from hub to tip to improve the efficiency. Wind energy has to compete with many other energy sources in future. To compete with others it had to cope with the least affirmative conditions to maximum positive conditions. Usual challenge for the turbines is performing at low wind speed. So far we have achieved 22rpm at 1.8m/s wind speed when the blades are wider and twisted by 120 degree. While twisted by 70 degree we got no rpm at 1.8m/s wind speed. It implies that the former condition produces better performance.

Renewable Energy Sources (RES) nowadays are integrated in a rapid way into power system and smart grids.Wind energy and in general RES penetration into power systems create several technical challenges and opportunities as well. In order the system stability and steady state operation to be ensured in power systems steady analysis and dynamic analysis are necessary. These configurations are applied in this study for load flow and transient stability analysis. IEEE 9-bus system is integrated with a Doubly-Fed Induction Generator Wind Farm and a three-phase fault is applied in a load bus. The aim and objective of this study is the behavior of IEEE 9-bus system with a DFIG Wind Farm during disturbances. Moreover critical fault clearing time is identified in this study for the corresponding three-phase fault. This study/work is conducted with the help of
PSS/E 34 software simulation tool of Siemens.

Increasing number of billboard collapse during wind storms indicates the vulnerability of this structure subjected to wind force. Typical billboard structures have fundamental natural frequency about 1 Hz or higher. Therefore, all previous studies assumed that the dynamic response of billboard structure is dominated by quasi-static response. However, billboard structures may contain damping values low enough to provoke significant resonant response. Moreover, dynamic wind load can lead billboard structures to oscillate in the along-wind and torsional direction. Coupling of these two responses may give net stress at the supporting column of billboard structure higher than allowable limit. A rigid 1:100 scale pressure model of a billboard structure was tested at TU-AIT wind tunnel under simulated open terrain boundary layer wind flow. Dynamic response of the billboard structure to wind-induced drag force and torsion was obtained individually. Thereafter, significance of resonant response was determined and lateral-torsional coupled displacement response was calculated by numerically joining individual responses. Lastly, equivalent static force for all wind attack angles were applied to finite element model and stress at supporting column was obtained through analysis. The results obtained from this study showed that dynamic response to wind-induced torsion of billboard structure is dominated by resonant response. However, high aerodynamic damping suppressed resonant response to wind-induced drag force. Though, lateral-torsional coupled displacement response is found to be indistinguishable to translational response. Yet, this inconsequential response results in higher net stress than allowable limit at the supporting column of billboard structure.

ASCE - SEI Performance-Based Wind Design is a Prestandard for Performance-Based Wind Design developed by the Structural Engineering Institute (SEI) of the American Society of Civil Engineers (ASCE) presents a recommended alternative
to the prescriptive procedures for wind design of buildings contained in the nationally adopted
standard Minimum Design Loads and Associated Criteria for Buildings and Other Structures
(ASCE 7) and in the International Building Code (IBC)