Significant progress has been made towards developing an effective solution method for predicting low-speed flows through vertical-axis wind turbines. A Godunov-type finite-volume scheme has been developed for the solution of the Euler equations in two-dimensions on a multi-block mesh. The proposed algorithm features a parallel block-based adaptive mesh refinement scheme and a mesh adjustment procedure to enable straightforward meshing of irregular solid boundaries. A low-Mach-Number preconditioner is used in conjunction with a dual timestepping scheme to reduce the computational costs of simulating low-speed unsteady flows. A second-order backwards differencing time-marching scheme is used for the outer physicaltime discretization, and an explicit optimally-smoothing multi-stage time-stepping scheme with multigrid acceleration is used for the inner pseudo-time loop. Results are presented for various low-speed flows that demonstrate the suitability of the algorithms for wind turbine flows. Additional theory and discussion are also presented for extension of the schemes to the full Navier-Stokes equations.

Significant progress has been made towards developing an effective solution method for predicting low-speed flows through vertical-axis wind turbines. A Godunov-type finite-volume scheme has been developed for the solution of the Euler equations in two-dimensions on a multi-block mesh. The proposed algorithm features a parallel block-based adaptive mesh refinement scheme and a mesh adjustment procedure to enable straightforward meshing of irregular solid boundaries. A low-Mach-Number preconditioner is used in conjunction with a dual timestepping scheme to reduce the computational costs of simulating low-speed unsteady flows. A second-order backwards differencing time-marching scheme is used for the outer physicaltime discretization, and an explicit optimally-smoothing multi-stage time-stepping scheme with multigrid acceleration is used for the inner pseudo-time loop. Results are presented for various low-speed flows that demonstrate the suitability of the algorithms for wind turbine flows. Additional theory and discussion are also presented for extension of the schemes to the full Navier-Stokes equations.

During 2006 and 2007 behavioral observations surveys of raptors were conducted at 12 turbines of a 66-turbine wind farm near Port Burwell, Ontario, Canada. Mortality surveys were conducted at all turbines in the wind farm with additional search effort at the twelve turbines where behavioral monitoring was conducted. The wind farm is located along a significant autumn raptor migration corridor along Lake Erie which is in the area of the Central Flyway. Only one raptor fatality was found each year at the 12 turbines used in the study, with one additional fatality found at the other 54 turbines in the wind facility. The estimated mortality rate for Erie Shore Wind Farm ranged from 0.028 to 0.049 raptor fatalities/MW/autumn. The estimated mortality rate for Erie Shores is at the low end of mortality for North American wind facilities outside of California, and which are not located in known migratory pathways. My findings suggest that the presence of high numbers of migrant raptors passing over a wind facility site does not automatically equate to high collision mortality. Over 5,579 observations of individual raptor passes within 250m of a turbine were recorded. The majority of raptors (73%) passed outside of blade sweep height. The majority of raptors avoided entering the risk zone of operational turbines with 2.92% (n = 159) of raptors observed passing within the risk zone of blade sweep height above ground and 0-40m out from the turbine base. The majority (73%) of raptors that entered the risk zone did so under conditions when risk was reduced due to turbine blade orientation in relation to the raptors’ direction of movement or when the turbine was not operational.

Aeroacoustic emissions were identified as a primary concern in the public acceptance of wind turbines. A review of literature involving sound localization was undertaken and led to the design of two microphone arrays to identify acoustic sources. A small-scale array composed of 27 sensors was produced with the intention of improving the quality of sound measurements over those made by a single microphone in a small, closed-loop wind tunnel. A large-scale array containing 30 microphones was also implemented to allow for measurements of aeroacoustic emissions from airfoils and rotating wind turbines. To minimize cost and pursue alternative sensor technologies, microelectromechanical microphones were selected for the array sensors and assembled into the arrays on printed circuit boards. Characterization of the microphones was completed using a combination of calibration techniques, primarily in a plane wave tube. Array response to known sources was quantified by analyzing source maps with respect to source location accuracy, beamwidth, and root mean square error. Multiple sources and rotating sources were tested to assess array performance. Following validation with known sources, wind tunnel testing of a 600 watt wind turbine was performed at freestream speeds of 2.5 m/s, 3.5 m/s, 4.5 m/s, and to 5.5 m/s. Significant aeroacoustic emissions were noted from the turbine in the 4.5 m/s and 5.5 m/s cases, with an increase of up to 12 dB over background levels. Source maps from the 5.5 m/s tests revealed that the primary location of aeroacoustic emissions was near the outer radii of the rotor, but not at the tip, and generally moved radially outward with increasing frequency. The azimuthal location of the greatest sound pressure levels was typically found to be between 120º and 130º measured counterclockwise from the upward vertical, coinciding with the predicted location of greatest emissions provided by an analytical model based on dipole directivity and convective amplification. Analysis of the acoustic spectra, turbine operating characteristics, and previous literature suggested that the sound emissions emanated from the trailing edge of the blades.

Thesis (M.Sc. (Hons)) -- University of Western Sydney, 2000. / "Thesis submitted to the University of Western Sydney, Nepean for the degree of Master of Engineering (Hons)" "School of Mechatronics, Computer and Electrical Engineering, December 2000" Includes bibliographical references (leaves 111-113).

Thesis (M. S.)--Mechanical Engineering, Georgia Institute of Technology, 2008. / Committee Chair: Shelton, Samuel; Committee Member: Bras, Berdinus; Committee Member: Jeter, Sheldon.

Thesis (doctoral)--Tallinn University of Technology, 2009. / Includes bibliographical references.

Thesis (Ph. D.)--Missouri University of Science and Technology, 2009. / Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed May 27, 2009) Includes bibliographical references (p. 126-130).

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.

Σκοπός της παρούσας διπλωματικής είναι η εξέταση των προτεινόμενων συστημάτων γείωσης για ανεμογεννήτριες σύμφωνα με την IEC και η προσομοίωση με Matlab της συμπεριφοράς τους σε πλήγμα κεραυνού στην κατασκευή μέσω της μεθόδου FDTD. Στο πρώτο κεφάλαιο αναπτύσσεται σύντομα το φαινόμενο του κεραυνού και οι ανανεώσιμες πηγές ενέργειας. Στη συνέχεια δίνονται στοιχεία για την αιολική ενέργεια και την εκμετάλλευσή της στον κόσμο και στην Ελλάδα. Επίσης αναλύονται τα βασικά μέρη και η λειτουργία μιας ανεμογεννήτριας. Στο δεύτερο κεφάλαιο αναλύεται η αντικεραυνική προστασία ανεμογεννητριών όπως προτείνεται στο διεθνές πρότυπο IEC-61024 και η διαδικασία αξιολόγησης της επικινδυνότητας μιας τέτοιας κατασκευής. Δίνονται οι βασικοί ορισμοί για συστήματα γείωσης. Διεξοδικότερα εξετάζονται οι δύο τύποι συστημάτων γείωσης για ανεμογεννήτριες, σύμφωνα πάντα με την IEC. Στο τρίτο κεφάλαιο αναλύεται η μέθοδος FDTD (Finite Difference Time Domain ) και ο αλγόριθμος του Yee. Η καινοτομία του αλγορίθμου αυτού ήταν η γεωμετρική απεικόνιση για τη δειγματοληψία των τιμών του ηλεκτρικού και του ηλεκτρομαγνητικού πεδίου η οποία αντιπροσωπεύει τις ολοκληρωτικές και τις διαφορικές μορφές των εξισώσεων του Maxwell. Για την προσομοίωση χρησιμοποιήθηκε επίσης η μέθοδος λεπτού αγωγού (thin wire) η οποία επιτρέπει την ακριβή μοντελοποίηση ενός λεπτού αγωγού(όπου λεπτός αγωγός ορίζεται ως αγώγιμο καλώδιο η ακτίνα του οποίου είναι μικρότερη από το μέγεθος του κελιού που χρησιμοποιεί η FDTD) και περιγράφεται στη συνέχεια του κεφαλαίου. Στο τέταρτο κεφάλαιο εξετάζουμε δυο προτεινόμενες διατάξεις γείωσης σύμφωνα με το πρότυπο της IEC. Εξηγείται αναλυτικά πως υλοποιήθηκε ο αλγόριθμος FDTD στο Matlab και αναφέρονται οι παραδοχές που έγιναν για τη σύγκλιση της μεθόδου .Παρουσιάζεται με γραφική απεικόνιση από το MAtlab η μοντελοποίηση του χώρου για τις 2 διατάξεις. Μελετάμε την αύξηση δυναμικού ,την βηματική τάση και την μεταβατική αντίσταση για τη διάταξη τύπου Α με ένα κάθετο ηλεκτρόδιο . Εξετάζουμε πως επηρεάζει τα παραπάνω μεγέθη η μεταβολή του βάθους του ηλεκτροδίου και πως μεταβάλλονται σε διαφορετικούς τύπους εδαφών. Ακόμα εξετάζουμε την συμπεριφορά ενός συστήματος γείωσης για τη διάταξη τύπου Β με ένα οριζόντιο δακτύλιο και τέσσερα κάθετα ηλεκτρόδια συγκριτικά με τη διάταξη Α. Στο τελευταίο κεφάλαιο σχολιάζονται τα αποτελέσματα των προσομοιώσεων και γίνεται σύγκριση των δύο προτεινόμενων διατάξεων γείωσης από την IEC. Συνοψίζονται τα πλεονεκτήματα και τα μειονεκτήματα της μεθόδου FDTD για προσομοίωση συμπεριφοράς συστημάτων γείωσης σε πλήγμα κεραυνού. Επίσης προτείνονται διαφορετικές προσεγγίσεις στην υλοποίηση της μεθόδου για την αντιμετώπιση των μειονεκτημάτων. / The subject of this essay is the analysis of the suggested by IEC grounding systems for wind turbines and the simulation of these systems using the FDTD method .The software used for the simulations was MATLAB. First chapter is a brief but essential theoretical approach on the lightning phenomenon. Moreover facts and figures are given for renewable energy and particularly wind power in Greece and worldwide. Furthermore the components and the function of a wind turbine are analyzed. The second chapter is a thorough study of the lightning protection systems for wind turbines as suggested by the international standard IEC-61204.The standard defines the risk assessment process of a wind turbine. The components of grounding systems are introduced and the two types of grounding systems for wind turbines according to IEC are analyzed. FDTD (Finite Difference Time Domain) method is analyzed in the third chapter along with Yee’s algorithm. The novelty of this method is the geometrical representation of the electrical and magnetic fields and the equations of Maxwell. The thin wire method was also used for the simulation in order to model precisely the conductors (as thin wire we define a wire with radius smaller than the cell used in the FDTD) and is described in this chapter. Along with writing this essay various grounding systems were simulated with MATLAB. In the forth chapter some brief comments about the development of the simulation are stated along with the description of the FTDT algorithm implementation. We study the potential rise, the step voltage and the transient resistance for the two types of grounding systems suggested by IEC and we observe how the depth of the rods and the resistivity of the soil affect them. In addition to that we also examine some variations of the two types of grounding systems in order to conclude to the optimal grounding system for a wind turbine. In the last chapter results are examined and conclusion are extracted and presented. The suggested by the IEC grounding systems are compared. Further optimizations of the simulation process are discussed leading to possible, future improvement. The advantages and disadvantages of the FTDT method for simulation of grounding systems after a lightning are presented.