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Η παρούσα διπλωματική εργασία πραγματεύεται τη μελέτη της επίδρασης ενός αιολικού συστήματος στην ευστάθεια ενός κοινού συστήματος ηλεκτρικής ενέργειας κατά τη λειτουργία της μόνιμης κατάστασης. Πιό συγκεκριμένα: Στο πρώτο κεφάλαιο γίνεται μία εισαγωγή σχετικά με την χρήση της αιολικής ενέργειας από τα παλαιά χρόνια έως και σήμερα, αλλά και στοιχείων που αφορούν τόσο την Ελλάδα αλλά και άλλες χώρες. Στο δεύτερο κεφάλαιο αναλύονται τα αιολικά συστήματα ως προς τη δομή τους, τη λειτουργία τους, τα προβλήματα που προκαλούν αλλά και τα οφέλη που αποφέρουν. Στο τρίτο κεφάλαιο ακολουθεί μία κατηγοριοποίηση των συστημάτων ανεμογεννητριών ως προς τον τύπο γεννήτριας που περιέχουν αλλά και τον τρόπο λειτουργίας τους. Στο τέταρτο κεφάλαιο γίνεται ανάλυση της διείσδυσης της αιολικής ενέργειας ως προς την κλίμακα διείσδυσης (μικρή – μεγάλη), τις προϋποθέσεις σωστής χρησιμοποίησής τους καθώς και των προβλημάτων που προκύπτουν σχετικά με την ευστάθεια τάσης αλλά και τη συχνότητα. Στο πέμπτο κεφάλαιο περιγράφεται η ανάλυση ροής φορτίου και πίο συγκεκριμένα η μέθοδος Newton-Raphson που χρησιμοποιήσαμε για την πραγματοποίηση του πειραματικού κομματιού αυτής της εργασίας. Στο έκτο κεφάλαιο παρουσιάζονται οι προσομοιώσεις που πραγματοποιήσαμε μαζί με τα αποτελέσματα που προέκυψαν. Τέλος στο έβδομο κεφάλαιο ακολουθεί σχολιασμός των παραπάνω αποτελεσμάτων. / This diploma thesis examines the influence of a wind energy system on the stability of a common electric power system during the steady state operation. More specifically: In the first chapter, there is an introduction related to the usage of wind energy from the past years up to nowadays, and also facts related not only to Greece but also other countries. In the second chapter, the wind energy systems are analyzed for their structure, the way they operate, the problems they cause and the benefits they yield. In the third chapter, there is a categorization of the wind energy systems in terms of the generator type the use and the state they operate. In the fourth chapter, there is an analysis of the wind power integration depending on the integration scale (small-scale – large-scale), the conditions of correct usage, as well as the problems that appear and are related to the voltage stability and the frequency. In the fifth chapter, the load flow procedure is described and more particularly the Newton-Raphson procedure that was used in this case. Ιn the sixth chapter, the simulation is presented along with the results. Finally, in the seventh chapter there are comments related to the results above.

Η παρούσα διπλωματική εργασία πραγματεύεται τη μελέτη μιας διάταξης ανεμογεννήτριας με επαγωγική μηχανή βραχυκυκλωμένου κλωβού η οποία συνδέεται μέσω dc διασύνδεσης με το δίκτυο. Τη dc διασύνδεση τη δημιουργεί ένας dc πυκνωτής και από την πλευρά της μηχανής υπάρχει ένας ac/dc πλήρως ελεγχόμενος ανορθωτής ισχύος ενώ από την πλευρά του δικτύου βρίσκεται ένας dc/ac πλήρως ελεγχόμενος αντιστροφέας ισχύος. Σκοπός της εργασίας είναι αρχικά να μελετήσουμε θεωρητικά το συνολικό σύστημα της ανεμογεννήτριας χρησιμοποιώντας το μετασχηματισμό Park για τη μοντελοποίηση του στο d-q πλαίσιο αναφοράς. Στη συνέχεια προχωρούμε στον υπολογισμό των εξισώσεων στο χώρο κατάστασης και τέλικά προτείνουμε ένα σύστημα ελέγχου το οποίο βασίζεται στους PI ελεγκτές. Τέλος, προσομοιώνουμε το παραπάνω σύστημα με τη βοήθεια της εφαρμογής Simulink του λογισμικού Matlab και μελετώντας τα αποτελέσματα, εξάγουμε τα ανάλογα συμπεράσματα. / The present thesis deals with the study of provision of wind generator with inductive machine of which is connected via dc interconnection with the network. A dc capacitor creates the dc interconnection with the network.The aim of this work is initially to study theoretically the total system of wind generator using the transformation Park for its modelling in the d-q frame of report. Afterwards we advance in the calculation of equations in the space of situation and finally we propose a system of control which is based on PI controllers. Finally, we simulate the system with the help of the Simulink application of Matlab and studying the results, we export the proportional conclusions.

Σκοπός της παρούσας διπλωματικής εργασίας είναι η μελέτη των παραγόντων που επηρεάζουν την αξιοπιστία και τη διαθεσιμότητα των αιολικών συστημάτων. Η επεξεργασία των ανεμολογικών δεδομένων (SCADA) έγινε από διάφορες εταιρείες, για να βοηθήσουν στην πρόβλεψη της ενεργειακής παραγωγής. Εξετάζονται επίσης τα διάφορα είδη βλαβών που συμβαίνουν στα αιολικά πάρκα, ειδικά τα πρώτα χρόνια λειτουργίας τους, και πώς ακριβώς μπορούμε να μειώσουμε το ποσοστό τους αν επέμβουμε σωστά. Τέλος, δίνονται χρήσιμες πληροφορίες για το βαθμό χρησιμοποίησης της αιολικής ενέργειας στην Ελλάδα και παγκόσμια. Πιο αναλυτικά, η δομή της εργασίας οργανώνεται στα εξής εννέα κεφάλαια: Το πρώτο κεφάλαιο ξεκινάει με γενικές πληροφορίες για τις ανανεώσιμες πηγές ενέργειας και γιατί η χρήση τους έγινε επιτακτική. Κατόπιν, γίνεται εξειδίκευση στην αιολική ενέργεια με μια ιστορική αναδρομή για να μπορέσει να δει κανείς την εξέλιξη της στο πέρασμα του χρόνου. Αναφέρονται επίσης τα πλεονεκτήματα της αιολικής ενέργειας, τα προβλήματα που προκύπτουν από την αξιοποίησή της καθώς και διάφορες λύσεις για την αντιμετώπισή τους. Στο δεύτερο και τρίτο κεφάλαιο εξετάζεται η βασικότερη παράμετρος που οδήγησε την αιολική ενέργεια στο στάδιο που είναι σήμερα, ο άνεμος. Αναλύεται η συμπεριφορά του, τα κύρια χαρακτηριστικά του και η κατανομή του. Το τέταρτο κεφάλαιο παρουσιάζει τις μονάδες που συμβάλλουν στη δέσμευση και εκμετάλλευση της αιολικής ενέργειας. Παρουσιάζονται με λεπτομέρεια τα δομικά τους στοιχεία και αναφέρονται οι κατηγορίες στις οποίες ανήκουν ανάλογα με τα χαρακτηριστικά τους. Αναφέρονται επίσης, οι βασικοί τρόποι λειτουργίας τους καθώς και οι παράμετροι που επηρεάζουν την επιλογή της τοποθεσίας εγκατάστασής τους. Στο πέμπτο κεφάλαιο εξετάζονται τα ενεργειακά χαρακτηριστικά των ανεμογεννητριών και παρουσιάζονται επίσης τα στοιχεία που επιδρούν στην αναμενόμενη ενεργειακή παραγωγή και στο κόστος της αιολικής ενέργειας. Στο έκτο κεφάλαιο, δίνονται γενικές πληροφορίες για τα αιολικά πάρκα, τη λειτουργία και τη συντήρησή τους καθώς και κάποιοι οικονομικοί παράγοντες όσον αφορά τα υπεράκτια αιολικά πάρκα. Στο έβδομο κεφάλαιο παρουσιάζονται τα αποτελέσματα της επεξεργασίας ανεμολογικών δεδομένων, ώστε να γίνουν κατανοητοί οι παράγοντες που επηρεάζουν και βελτιώνουν την αξιοπιστία των αιολικών συστημάτων. Στο όγδοο κεφάλαιο, εξετάζεται και αξιολογείται η διαθεσιμότητα των αιολικών συστημάτων, δίνονται πληροφορίες για τα διάφορα είδη της καθώς και διάφοροι τρόποι οι οποίοι συμβάλλουν στη βελτίωσή της, που είναι και το ζητούμενο για την οικονομική βιωσιμότητα του αιολικού πάρκου. Τέλος, στο ένατο κεφάλαιο, παρουσιάζεται η τρέχουσα κατάσταση στην Ελλάδα, στις χώρες της Ευρωπαϊκής Ένωσης αλλά και παγκόσμια. / The purpose of this diploma thesis is the study of factors that affect the reliability and availability of wind energy systems. Wind data from several companies were accumulated for a better prediction of the energy production. More specifically, the structure of the essay is organized in the following nine chapters : The first chapter starts with general information on renewable energy sources and the reasons why their use became imperative. Moreover, there is specialization in wind energy with a throwback which enables us to see the evolution of the passing of time. The second and third chapter examines the key parameters leading wind energy in its present form, the wind. The fourth chapter presents the system-units that contribute to the exploitation of wind energy. Their components are presented in detail, and the categories to which they belong are indicated according to their characteristics. The fifth chapter discusses the energy characteristics of the wind turbines and also presents the elements that affect the expected energy production and the cost of wind energy. In the sixth chapter, general information about wind farms are given, as well as information about operation, maintenance and some economic factors in offshore wind farms. The seventh chapter presents the results of wind data processing in order to understand the factors that influence and improve the reliability of wind systems. The eighth chapter examines and evaluates the availability of wind energy systems. Information about the different types of availability are given, and also details about the different ways which contribute to the improvement of availability are presented. Finally, the ninth chapter presents the current situation in Greece, the countries of the European Union and worldwide.

The purpose of this research is to propose a novel wind turbine for an omni-flow wind energy system and investigate its aerodynamic performance. The geometry of the novel wind turbine is based upon the impulse turbine technology which has been successful in wave energy. In this study, both numerical and experimental studies were conducted to evaluate the aerodynamic features of this wind turbine. The numerical method was validated by a comparison between numerical and experimental results over a range of tip speed ratios. Results obtained from experiments and simulations indicate that the proposed wind turbine can be employed. Additionally, on the basis of the analyses performed, this new wind turbine has the potential for having a good startup feature, which means that this wind turbine can be suitable for applications in an urban environment. As an important component, the stator of this wind turbine can increase the passing flow velocity by 20%. Meanwhile, the passing flow direction also can be optimised by the stator. Aerodynamics of the wind turbine was analysed under the non-uniform flow condition, because the flow is non-uniform inside the omni-flow wind energy system. It was found that the maximum power coefficient of such a turbine under the non-uniform flow condition is lower than that under the uniform flow condition. Due to the non-uniform flow, the blades experience different flow velocities, and as a consequence, undergo different aerodynamic loads during one operation cycle. Thus the generated torque and thrust on a blade are subjected to frequent and periodical changes. Influences of the geometrical parameters on the aerodynamic characteristics of this wind turbine were investigated. From the initial study, it was found that changes of hub-to-tip ratios, numbers of blades, aerofoils and numbers of guide vanes, can significantly affect the II power performance. Additionally, the wind turbine obtained high values of maximum torque coefficients with changing geometrical parameters.

[pt] A presente pesquisa trata da determinação experimental das eficiências e da simulação de desempenho de turbinas eólicas de eixo vertical do tipo Darrieus. Os testes foram efetuados usando-se modelos reduzidos num túnel. Um novo método para a obtenção da potência da turbina foi desenvolvido. O método clássico requereria grandes modelos e um grande túnel de vento para facilitar a medida do torque. Uma vez que as curvas características dos modelos reduzidos foram determinadas, numa forma adimensional, uma simulação de desempenho de turbinas em tamanho real foi desenvolvida. Tal simulação envolveu duas regiões brasileiras (Fortaleza e Fernando de Noronha) e o conhecimento da distribuição de ventos horária. / [en] The present research is concerned with the experimental determination of the efficiencies and performance simulation of Darrieus vertical-axis wind turbines. The tests were performed using reduced models in a wind tunnel. A new method for obtaining the turbine power was developed. The classical approach would require large models and a huge wind tunnel to facilitate the torque measurement. Once the characteristic curves of reduced models were determined, in a dimensionless form, a performance simulation of real size turbines was developed. Such a simulation involved two Brazilian regions (Fortaleza and Fernando de Noronha) and the knowledge of the hourly wind distribution.

The Scottish government’s aim of deriving 100 per cent of the nation’s electricity from renewable sources is dependent on the utilisation of wind energy. Social barriers, however, have continued to threaten these targets. Community benefit funds have often been paraded as the most common way of improving public attitudes towards wind farms in the United Kingdom, although little empirical evidence exists to support this notion. Using the proposed Ourack wind farm, approximately three and a half miles north of Grantown-on-Spey in the Scottish Highlands, this case study, consisting of a sequential explanatory research design comprised of an initial close-ended survey followed by in-depth semi-structured interviews, sought to explore the community’s perceptions of community benefits, identify the type of fund that the community wanted, and investigate the role of such benefit provisions in altering perceptions of wind farms. The key findings indicated that the majority of participants were in favour of benefits being provided, they preferred funding to be directed towards community organisations, and approximately one third of research participants (31.6 per cent) perceived the proposed wind farm in a more positive light after considering the possible benefits the region would accrue. Furthermore, the research indicated the need for community benefits to become a standardised part of the planning process, thus reducing the likelihood of financial benefits being perceived as bribes, and allowing developers to provide greater information about any proposed benefits scheme prior to applying for planning permission. There are implications of this study for academics researching the role of community benefits in wind farm planning, and policymakers and developers for understanding the wants and needs of community members.

The growing need for reducing the negative impacts of climate change and ensuring a constant and environmentally friendly energy supply, led the way to the exploitation of renewable energy sources. Canada has already acknowledged this trend by incorporating more power from renewables on its energy mix. Similarly, Nova Scotia has started an ambitious energy program in which the substitution of most of the fossil fuels by wind energy, will play a significant factor. The purpose of this research is to investigate all suitable locations for wind energy development in the province of Nova Scotia, under the scope of minimizing environmental impacts, increasing social acceptance and maximizing energy production. This spatial analysis is performed through the combination of Geographical Information Systems (GIS) and a Multi Criteria Decision Analysis (MCDA). The analysis of the province was based on the preferences of wind experts and administration authorities, which formed the weights assigned on eight (8) evaluation criteria. The extract of the relative weights was succeeded by using the Analytical Hierarchy Process (AHP), while their spatial dimensions were expressed by GIS software. The above procedure was possible through the application of a methodology where exclusion areas were found on the first place and the remaining areas were assessed on their level of suitability. The implementation of the GIS-MCDA methodological framework indicates that, despite the exclusion of a significant part of the province, there is still enough space to develop wind energy. The applied methodology and relevant results could be used as a Decision-Making tool by planning authorities, wind developers, and stakeholders.

Rapid deployment of terrestrial wind power plants (WPPs) is a function of accurate identification of areas suitable for WPPs. Efficient WPP site prospecting not only decreases installation lead time, but also reduces site selection expenses and provides faster reductions of greenhouse gas emissions. Combining conventional predictor variables, such as wind strength and proximity to transmission lines, with nonconventional socioeconomic and demographic predictor variables, will result in improved identification of suitable counties for WPPs and therefore accelerate the site prospecting phase of wind power plant deployment. Existing and under-construction American terrestrial WPPs located in the top 12 windiest states (230 as of June 2009) plus 178 potential county level predictor variables are introduced to logistic regression with stepwise selection and a random sampling validation methodology to identify influential predictor variables. In addition to the wind resource and proximity to electricity transmission lines, existence of a Renewable Portfolio Standard, the population density within a 200 mile radius of the county center, median home values, and farm land area in the county are the four strongest nonconventional predictors (Hosmer and Lemeshow Chi-Square = 9.1250, N = 1009, df = 8, p = 0.3319, - 2LogLikelihood = 619.521). Evaluation of the final model using multiple statistics, including the Heidke skill score (0.2647), confirms overall model predictive skill. The model identifies the existence of 238 suitable counties in the twelve state region that do not possess WPPs (~73% validated overall accuracy) and eliminates 654 counties that are not classified as suitable for WPPs. The 238 counties identified by the model represent ideal counties for further exploration of WPP development and possible transmission line construction. The results of this study will therefore allow faster integration of renewable energy sources and limit climate change impacts from increasing atmospheric greenhouse gas concentrations.