This thesis analyzes the feasibility of having an integrated wind and solar farm to optimize the use of land resources and capital investment by evaluating the effect that wind turbine shadows have on the area surrounding them. Two methods are used to predict shadow impact. The first method is based on the traditional textbook “Clear Sky” equations, which have maximum sensitivity to shadows because the method considers every day to be a perfect day. The second method uses measured global-horizontal and diffuse-horizontal solar radiation in units of W/m2, which take into account the true variations of daily conditions. The calculations are performed for 1 square meter surfaces, over different assumed areas of a wind power plant, for every second of the day. For purposes of shadow calculations, the tip-top height (i.e., tower height plus blade length) is used. All calculations are performed with the specifications of a GE 1.5 MW wind turbine, which is the most commonly used wind turbine in USA. / text

The rapid growth in the number of large wind farms has raised serious concerns about their effects on existing radar systems. The large size and rotational movement of the turbine blades can give rise to significant Doppler clutters, which interfere with the detection of moving targets such as aircraft and storms. A previous Air Force study has collected and analyzed the time-varying radar cross section resulting from the blade rotation of a single 1.5 MW turbine. However, multiple interactions taking place in a turbine were not studied in detail. Multiple interactions could play an important role in the propagation of radar signals through wind farms. This thesis sets out to more closely examine the various Doppler features resulting from the scattering due to a single turbine. Backscattered and forward scattered data are measured at Ku-band from various wind turbine models using a motorized turntable in the laboratory. The tested models include a 1:160 scale model turbine, a 3-arm wire model turbine, and a small wind turbine from Bergey Windpower with 2’ blades. The data are processed based on the short-time Fourier transform in order to relate the resulting time-varying Doppler features to various scattering mechanisms. The experimental findings are corroborated by simulations performed using the Numerical Electromagnetics Code (NEC). Furthermore, we propose a post-processing general method to reduce the intensity of the turbine scattered data. This method is applied to filter out simulated Doppler clutter from two different simulation techniques. First, the method is applied to remove the simulated Doppler clutter from the point scatterer model. Next, the algorithm is applied to simulated backscattered data generated using a high-frequency ray tracing code, Ahilo. / text

While wind energy has witnessed faster growth than any other renewable energy source in recent years, two issues—the decreasing availability of large land expanses for new wind farms and transmission difficulties arising from siting wind farms in remote regions far from load centers—have slowed down this growth considerably. Siting wind turbines offshore places the generating capacity closer to population and load centers; thus, reducing grid congestion. Also, at offshore sites, one can expect higher wind speeds, decreased turbulence, and reduced noise and visual impact constraints. Offshore wind turbines that have been built thus far have had foundations (such as monopiles or jacket structures) that have extended to the seabed. Such offshore wind turbines have thus been confined to shallow waters closer to the shore. Sites farther offshore provide better wind resources (i.e., less turbulence and smoother, stronger winds) while also reducing visual impact, noise, etc. However, deeper waters encountered at such sites make bottom-supported turbines less economical. Wind turbines mounted atop floating platforms are, thus, being considered for deeper water offshore sites. Various floating platform concepts are under consideration; the chief differences among them arise from the way they provide stability to counter the large mass of the rotor-nacelle assembly located high above the mean water level. Of these alternative concepts, the spar buoy platform is a deep draft structure with a low center of gravity, below the center of buoyancy. Reliability analysis of a spar buoy-supported floating offshore 5MW wind turbine based on stochastic simulation is the subject of this study. Environmental data from a selected deepwater reference site are employed in the numerical studies. Using time-domain simulations, the dynamic behavior of the coupled platform-turbine system is studied; statistics of tower and rotor loads as well as platform motions are estimated and critical combinations of wind speed and wave height identified. / text

Σκοπός είναι η διερεύνηση της τεχνολογίας των χερσαίων (onshore) ανεμογεννητριών και συγκεκριμένα των πυλώνων των ανεμογεννητριών. Αν εξετάσουμε το αιολικό δυναμικό στις χερσαίες περιοχές της Ευρώπης, παρατηρούμε αμέσως τις τεράστιες δυνατότητες ανάπτυξης ανεμογεννητριών. Παρατηρούμε επίσης την πλεονεκτική θέση της χώρας μας που εμφανίζεται να διαθέτει στο Αιγαίο πέλαγος μια από τις πλουσιότερες, σε αιολικό δυναμικό, περιοχές της Ευρώπης. Για να έχουμε όμως μεγαλύτερη απόδοση στην ισχύ μιας ανεμογεννήτριας πρέπει να αυξήσουμε το ύψος της έτσι ώστε να εκμεταλλευτούμε τις υψηλότερες ταχύτητες ανέμου σε μεγαλύτερα ύψη. Αυτό με την σειρά του θα επιφέρει πιο μεγάλα φορτία και επομένως μεγαλύτερες καταπονήσεις (εντατικά μεγέθη) στην βάση του πυλώνα καθώς η ανεμογεννήτρια προσομοιώνεται με σύστημα προβόλου. Ως συνέπεια τούτου θα πρέπει να αυξήσουμε την αντοχή του πυλώνα είτε αυξάνοντας το πάχος του υλικού της διατομής (αποφεύγεται – απαιτούνται μεγάλα πάχη συνεπώς μεγάλα κόστη), είτε αυξάνοντας τη διάμετρο της διατομής (αποφεύγεται – περιορισμένο πλάτος οδικού δικτύου που αποτρέπει την μεταφορά τμημάτων του πυλώνα της ανεμογεννήτριας με μεγάλες διατομές), είτε αυξάνοντας την αντοχή του υλικού της διατομής (αντικείμενο διατριβής). Στην παρούσα διατριβή γίνεται μελέτη βελτιστοποίησης σχεδιασμού των πυλώνων των ανεμογεννητριών με σύμμικτη διατομή χάλυβα-σκυροδέματος η οποία οδηγεί σε σχετικά μικρά πάχη διατομών, μικρής διαμέτρου, μεγάλης επιθυμητής αντοχής και μειωμένου κόστους υλικά. Αρχικά γίνεται η ανάλυση διατομής με στόχο την βελτιστοποίηση - ελαχιστοποίηση του κόστους για δεδομένη αντίσταση και στη συνέχεια η ανάλυση επαναλαμβάνεται για την βελτιστοποίηση του κόστους για δεδομένη δυσκαμψία. Στη συνέχεια με τη βοήθεια του σχεδιαστικού αναλυτικού προγράμματος ANSYS θα γίνει η σχεδίαση του πυλώνα της ανεμογεννήτριας όπου θα εφαρμοστούν τα προβλεπόμενα φορτία. Κατόπιν αυτού του σχεδιασμού διεξάγουμε πείραμα στο εργαστήριο όπου προσομοιώνουμε την ανεμογεννήτρια ώστε να συγκρίνουμε τα πειραματικά αποτελέσματα με την αναλυτική διαδικασία στο πρόγραμμα ANSYS. Γίνεται παράθεση και σχολιασμός των αποτελεσμάτων ώστε να προκύψουν τα συμπεράσματά μας και τελικώς γίνονται προτάσεις για περαιτέρω έρευνα όσον αφορά τα υλικά της διατομής των πυλώνων καθώς και την καλύτερη αξιοποίηση της αιολικής ενέργειας. / The aim is to investigate the technology of land (onshore) wind turbines and specifically for the pillars of wind turbines. If we investigate the wind potential in inland areas of Europe, we see immediately the enormous growth potential of wind turbines. We also observe the vantage point of our country that appears to have the Aegean Sea, one of the richest in wind potential areas of Europe. In order to increase the power of a wind turbine we must increase its height so as to take advantage of higher wind speeds at higher altitudes. This leads to higher loads and thus higher stresses (section forces) at the base of the tower as the wind turbine system is simulated with the cantilever system. As a consequence we should increase the strength of the pillar by increasing the thickness of the section material (to be avoided - large thicknesses therefore high costs required) or by increasing the diameter of the cross section (to be avoided - narrow road network that prevents transfer of the turbine pillar parts with large cross-sections), or by increasing the strength of the section’s material (subject of thesis). This thesis deal with the Design Optimization of Composite Cross Section Steel – Concrete Wind Turbine Towers which leads to relatively low thickness cross-sections, with small diameters, desirable high strength and reduced cost of materials. Initially we conduct sectional analysis in order to optimize - minimize the cost for a given resistance, and then the analysis is repeated for cost optimization for a given stiffness. Then we develop equations which correlate the moment, the stiffness and the cost of the wind turbine tower with the thicknesses of the materials (steel – concrete) which the cross section is composed of. Consequently we plot the equations that give the materials’ dimensions ranges when both the moment and stiffness is modified. Also we can understand how all this procedure affects the whole cost of the cross section. Then we conduct analysis and design of the wind turbine pillar with the analytical program ANSYS according to the design loads. Afterwards, lab-scale tests are conducted in order to model the wind turbine behavior. The experimental results are compared to the analytical observations. Finally we display and comment the results of that research so as to draw conclusions regarding the pillar design and the efficient wind energy utilization and present suggestions to future research.

Darbo metu apžvelgti vėjo energijos pagrindiniai parametrai. Atkreiptas dėmesys į vėjo kryptį ir jo įtaką generuojamos elektros energijos kiekiui. Trumpai apžvelgti vėjo išteklių įvertinimo būdai. Šiam tikslui naudojami matematiniai modeliai arba vėjo parametrų duomenų rinkimas pasirinktoje vietovėje. Įvertinami namų ūkio poreikiai tam tikru paros metu ir per metus. Darbo metu susipažinta su dabartine vėjo energetikos padėtimi ir plėtros galimybėmis Lietuvoje. Pateikiamos plėtros galimybės. Apžvelgta vėjo jėgainių tyrimo metodika ir pagrindiniai parametrai. Pasirinkus vėjo jėgainių skaičiavimo programą, atlikta šešių įvairios galios jėgainių skaičiavimai. Pagal aplinkos ir pasirinktos turbinos parametrus buvo apskaičiuotas vėjo turbinų pagamintas elektros energijos kiekis. Vėjo jėgainėje generuojamas energijos kiekis palyginamas su namų ūkio poreikiais ir pateikiama, kada apkrova yra tenkinama. Generuojamos elektros energijos dydis apskaičiuotas kas mėnesį visus metus. Pasinaudojant programa, buvo atlikta atsiperkamumo ir pagamintos elektros energijos optimalios kainos prognozė. Darbe atliktais tyrimais parodyta, kad tik pusė pasirinktų vėjo jėgainių atsiperka. Pateikiami naudingumo faktoriai, kurie parodo kiek laiko per metus procentais dirbs tokia vėjo jėgainė. / During the work was made an overview of the main parameters of wind energy. Attention is drawn to the wind direction and its influence on the amount of electricity generated. A brief overview was made of the wind resource assessment techniques. For this purpose, use of mathematical models and wind parameters collection of data in the target area. Assessed household needs certain time of day during the year. During acquainted with the current situation and wind energy development opportunities in Lithuania. Provided opportunities for development. Made an overview of wind power research methodology and main settings. Selected wind power calculation program conducted six different power plants calculations. According to the environment, and turbine parameters were calculated for wind turbines produced electricity. Wind power plant to generate energy comparable to household needs and provided, when the load is met. Generating electricity is calculated on a monthly basis throughout the year. Taking advantage of the program was carried out and the payback of electricity produced optimal price forecast. The paper studies showed that only half of the selected wind turbine pays off. Capacity factors are presented that shows how much percentage of time during the year will work the wind turbine.

Magistriniu darbu, kurio tema “Vertikalios ašies vėjo jėginės sparno modeliavimas“, siekiama ištirti mažos galios, paprastos konstrukcijos, vertikalios ašies vėjo jėgainės sparnuotes, atlikti jų kompiuterinį modeliavimą ir analizę. Tema yra aktuali dėl to, kad norint būti energetiškai nepriklausomiems, reikia ieškoti alternatyvių energijos šaltinių, kurie būtų neišsenkantys, prieinami daugeliui vartotojų. Vienas iš tokių - vėjo srauto energija, tačiau gyvenant tankiai užstatytoje, geografiškai šiurkščioje aplinkoje, tenka ieškoti mažų matmenų, mažos galios įrenginių, kurie pajėgtų dirbti esant mažiems vėjo greičiams ir sūkurinėmis sąlygomis, nedarkytų gamtos ar pastatų estetinės išvaizdos, nekeltų triukšmo ir būtų kuo lengviau aptarnaujami. Atliekant tyrimą, VAVJ sparno modelio analizės skaičiavimai buvo daromi remiantis bendrąja hidrodinaminių srautų teorija, naudojant baigtinių elementų analizės, projektavimo ir modeliavimo programą - COMSOL Multiphysics. Atlikti tyrimai parodė, kad didesnį sukimo momentą gausime naudodami uždarų galų rotorius, o įrengus oro srautą kreipiančias mentes, slėgis į rotoriaus sparną ženkliai išauga. Statant šachmatine tvarka keletą VAVJ, didžiausią slėgį į sparnuotes gausime esant 6 kartus didesniam atstumui nei sparnuočių spindulys. / The aim of this master's dissertation on the theme of "FEM modeling of vertical wind turbine using CFD solvers" is to investigate the low-power, simple design, vertical axis wind turbine impellers and to carry out their computer simulation and analysis. The theme is of great importance so as to be energectically independent, it is also necessary to look for alternative energy sources that are inexhaustible and accessible to many users. One of them - the wind flow energy, but living in a densely built-up, geographically rough environment forces us to look for small footprints, low-power devices that would be able to work at low wind speeds and eddy terms wouldn't damage natural and aesthetic appearance of the buildings making no noise and also maximize opportunities to be serviced. The study of VAWT wing pattern analysis calculations were made based on the general theory of hydrodynamic flows, using finite element analysis, as well as design and simulation software - COMSOL Multiphysics. Research has shown that we will get bigger torque while using closed ends of the rotors, and the installation of air flow directing vanes, the pressure in the rotor wing significantly increases. Constructing in a checkered order a few VAWT, the greatest pressure on the impellers receives 6 times greater distance than the impeller radius.

The geophysical technique known as Multichannel Analysis of Surface Waves, or MASW (Park et al., 1999) is a relatively new seismic characterisation method which utilises Rayleigh waves propagation. With MASW, the frequency dependent, planar travelling Rayleigh waves are created by a seismic source and then measured by an array of geophone receivers. The recorded data is used to image characteristics of the subsurface. This thesis explains how MASW was used as a geotechnical investigation tool on windfarms in the lower North Island, New Zealand, to determine the stiffness of the subsurface at each wind turbine site. Shear‐wave velocity (VS) profiles at each site were determined through the processing of the MASW data, which were then used to determine physical properties of the underlying, weathered greywacke. The primary research site, the Te Rere Hau Windfarm in the Tararua Ranges of the North Island, is situated within the Esk Head Belt of Torlesse greywacke (Lee & Begg, 2002). Due to the high level of tectonic activity in the area, along with the high rates of weathering, the greywacke material onsite is highly fractured and weathering grades vary significantly, both vertically and laterally. MASW was performed to characterise the physical properties at each turbine site through the weathering profile. The final dataset included 1‐dimensional MASW shear‐wave evaluations from 100 turbine sites. In addition, Poisson’s ratio and density values were characterised through the weathering profile for the weathered greywacke. During the geotechnical foundation design at the Te Rere Hau Windfarm site, a method of converting shear wave velocity profiles was utilised. MASW surveying was used to determine VS profiles with depth, which were converted to elastic modulus profiles, with the input parameters of Poisson’s ratio and density. This study focuses on refining and improving the current method used for calculating elastic modulus values from shear‐wave velocities, primarily by improving the accuracy of the input parameters used in the calculation. Through the analysis of both geotechnical and geophysical data, the significant influence of overburden pressure, or depth, on the shear wave velocity was identified. Through each of the weathering grades, there was a non‐linear increase in shear wave velocity with depth. This highlights the need for overburden pressure conditions to be considered before assigning characteristic shear wave velocity values to different lithologies. Further to the dataset analysis of geotechnical and geophysical information, a multiple variant non‐linear regression analysis was performed on the three variables of shear wave velocity, depth and weathering grade. This produced a predictive equation for determining shear wave velocity within the Esk Head belt ‘greywacke’ when depth and weathering data are known. If the insitu geological conditions are not comparable to that of the windfarm sites in this study, a set of guidelines have been developed, detailing the most efficient and cost effective method of using MASW surveying to calculate the elastic modulus through the depth profile of an investigation site.

The noise coming from wind power development can be an environmental impact forthe surrounding communities. It is well known that the main wind turbine noise iscaused by the movement of the turbine wings through the air. However, there areuncertainties about the importance of machinery sounds and possible variations amongwind turbines. A high resolution acquisition system was used to perform a fieldexperiment comparison of the noise spectra from some wind turbines at Laholm(Sweden). The results have shown different band spectra peaks associated to machinerysounds among wind turbines from the same model and also from those of differentmanufactures. Maintenance conditions of these wind turbines could explain thedifferences in intensity and frequency locations of the band spectra peaks found. Inorder to know the importance for human audition of these peaks, listening test or doseresponsestudies would be needed to provide relevant information in this regard. Themethodology developed in this study is suggested to be useful for identifying certainmachinery failures which could corrupt the noise sounds emitted at certain wind turbinelocations.

Alleviating loads on a wind turbine blades would allow a reduction in weight, and potentially increase the size and lifespan of rotors. Trailing edge flaps are one technology proposed for changing the aerodynamic characteristics of a blade in order to limit the transformation of freestream wind fluctuations into load fluctuations within the blade structure. An instrumented wind turbine test rig and rotor were developed to enable a wide-range of experimental set-ups for such investigations. The capability of the developed system was demonstrated through a study of the effect of stationary trailing edge flaps on blade load and performance. The investigation focused on measuring the changes in flapwise bending moment and power production for various trailing edge flap parameters. The blade was designed to allow accurate instrumentation and customizable settings, with a design point within the range of wind velocities in a large open jet test facility. The wind facility was an open circuit wind tunnel with a maximum velocity of 11m/s in the test area. The load changes within the blade structure for different wind speeds were measured using strain gauges as a function of flap length, location and deflection angle. The blade was based on the S833 airfoil and is 1.7 meters long, had a constant 178mm chord and a 6o pitch. The aerodynamic parts were 3D printed using plastic PC-ABS material. The total loading on the blade showed higher reduction when the flap was placed further away from the hub and when the flap angle (pitching towards suction side) was higher. The relationship between the load reduction and deflection angle was roughly linear as expected from theory. The effect on moment was greater than power production with a reduction in moment up to 30% for the maximum deflection angle compared to 6.5% reduction in power for the same angle. Overall, the experimental setup proved to be effective in measuring small changes in flapwise bending moment within the wind turbine blade.

Expectations for turbine-mounted lidar are increasing. The installation of lidars in wind turbine nacelles for measuring incoming winds, preventing wind gusts and increasing energy productions is after recently studies, technically and economically feasible. Among available lidar types, the most studied were continuous wave lidars because they were the most reliable apparatus when this initiative began. However, after studying technical considerations and checking commercial lidars, it was found that pulsed lidarslead this technology due to their promising results. The purpose of this report is to fill the gap between the interest in this technology and the absence of any academic papers that analyzes continuous-wave and pulsed lidars forthe mounted lidar concept. Hence, this report discusses the importance of turbine mounted lidars for wind power industry, different possible configurations and explains why specifically pulsed lidars are becoming more important for the mounted lidarmarket.