Wind Farm Noise: Measurement, Assessment by Colin H. Hansen, Con J. Doolan, and Kristy L. Hansen

6459755ebe32ec9-261x361.jpg Author Colin H. Hansen, Con J. Doolan, and Kristy L. Hansen
Isbn 9781118826065
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Year 2017
Pages 624
Language English
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Category physics


Wiley Series in Acoustics, Noise and Vibration: Wind Farm Noise The Effects of Sound on People Hansen Cowan February 2017 May 2016 Engineering Vibroacoustic Analysis: Methods and Applications Hambric et al April 2016 Formulas for Dynamics, Vibration and Acoustics Blevins November 2015 Wind Farm Noise: Measurement, Assessment and Control Colin H. Hansen School of Mechanical Engineering University of Adelaide Australia Con J. Doolan School of Mechanical and Manufacturing Engineering University of New South Wales Australia Kristy L. Hansen School of Computer Science, Engineering and Mathematics Flinders University Australia This edition first published 2017 © 2017 John Wiley & Sons Ltd Registered Office John Wiley & Sons Ltd, The Atrium, Southern Gate, Chichester, West Sussex, PO19 8SQ, United Kingdom For details of our global editorial offices, for customer services and for information about how to apply for permission to reuse the copyright material in this book please see our website at The right of the author to be identified as the author of this work has been asserted in accordance with the Copyright, Designs and Patents Act 1988. All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, except as permitted by the UK Copyright, Designs and Patents Act 1988, without the prior permission of the publisher. Wiley also publishes its books in a variety of electronic formats. Some content that appears in print may not be available in electronic books. Designations used by companies to distinguish their products are often claimed as trademarks. All brand names and product names used in this book are trade names, service marks, trademarks or registered trademarks of their respective owners. The publisher is not associated with any product or vendor mentioned in this book. Limit of Liability/Disclaimer of Warranty: While the publisher and author have used their best efforts in preparing this book, they make no representations or warranties with respect to the accuracy or completeness of the contents of this book and specifically disclaim any implied warranties of merchantability or fitness for a particular purpose. It is sold on the understanding that the publisher is not engaged in rendering professional services and neither the publisher nor the author shall be liable for damages arising herefrom. If professional advice or other expert assistance is required, the services of a competent professional should be sought. Library of Congress Cataloging-in-Publication Data Names: Hansen, Colin H., 1951- author. | Doolan, Con J., author. | Hansen, Kristy L., author. Title: Wind farm noise : measurement, assessment and control / Colin H. Hansen, Con J. Doolan, Kristy L. Hansen. Description: Hoboken : John Wiley & Sons Inc., [2017] | Includes bibliographical references and index. Identifiers: LCCN 2016036077| ISBN 9781118826065 (cloth) | ISBN 9781118826126 (epub) | ISBN 9781118826119 (Adobe PDF) Subjects: LCSH: Wind power plants–Noise. Classification: LCC TK1541 .H26 2017 | DDC 621.31/2136–dc23 LC record available at A catalogue record for this book is available from the British Library. Cover Image: Gettyimages/Dazzo Set in 10/12pt, WarnockPro by SPi Global, Chennai, India 10 9 8 7 6 5 4 3 2 1 This book is dedicated to our families without whose patience it may not have been completed. There are three sides to every story: your side, my side and the truth. And no-one is lying. Robert Evans, an American film producer born June 29, 1930. If we knew what it was we were doing, it wouldn’t be called research, would it? Albert Einstein commenting on research. Clever is the person who believes half of what he hears. Brilliant is the person who chooses the right half to believe.… vii Contents Wiley Series in Acoustics, Noise and Vibration xv Preface xvii 1 Wind Energy and Noise 1 1.1 1.2 Introduction 1 Development of the Wind Energy Industry 2 1.2.1 Early Development Prior to 2000 2 1.2.2 Development since 2000 8 1.2.3 Support Received by the Wind Industry 11 History of Wind Turbine Noise Studies 13 1.3.1 Modern Wind Turbine Sound Power Levels 16 Current Wind Farm Noise Guidelines and Assessment Procedures 18 1.4.1 ETSU-R-97 (used mainly in the UK and Ireland) 18 1.4.2 National Planning Policy Framework for England 25 1.4.3 World Health Organisation Guidelines 25 1.4.4 DEFRA Guidelines 27 1.4.5 Noise Perception Index 28 Wind Farm Noise Standards 29 1.5.1 General Environmental Noise Standards 29 1.5.2 IEC 61400-11 29 1.5.3 NZS6808 31 1.5.4 AS4959 31 Regulations 32 1.6.1 What Should be Included in a Wind Farm Noise Regulation 32 1.6.2 Existing Noise Ordinances and Regulations 38 Inquiries and Government Investigations 43 1.7.1 Australia 2010–2014 43 1.7.2 Canada 48 1.7.3 Denmark 2013 50 1.7.4 Northern Ireland 2013 51 1.7.5 Scotland 51 1.7.6 Wales 51 Current Consensus on Wind Farm Noise 52 References 52 1.3 1.4 1.5 1.6 1.7 1.8 viii Contents 2 Fundamentals of Acoustics and Frequency Analysis 57 2.1 2.2 Introduction 57 Basic Acoustics Concepts 57 2.2.1 Root Mean Square Sound Pressure 58 2.2.2 Statistical Descriptors and Their Use 59 2.2.3 Amplitude, Frequency, Wavelength, Wavenumber and Speed for Single-frequency Sound 60 2.2.4 Units for Sound Pressure Measurement 62 2.2.5 Sound Power 63 2.2.6 Beating 64 2.2.7 Amplitude Modulation and Amplitude Variation 66 2.2.8 Decibel Addition 69 2.2.9 Decibel Subtraction 70 2.2.10 Noise Source Directivity 71 2.2.11 Weighting Networks 71 2.2.12 Noise Level Measures 73 2.2.13 Sound in Rooms 76 Basic Frequency Analysis 79 2.3.1 Digital Filtering 82 2.3.2 Octave Band and 1/3-Octave Band Analysis 83 2.3.3 Octave and 1/3-Octave Filter Rise and Settling times 84 Advanced Frequency Analysis 88 2.4.1 Auto Power Spectrum and Power Spectral Density 91 2.4.2 Linear Spectrum 95 2.4.3 Leakage 95 2.4.4 Windowing 96 2.4.5 Sampling Frequency and Aliasing 103 2.4.6 Overlap Processing 103 2.4.7 Zero Padding 105 2.4.8 Uncertainty Principle 105 2.4.9 Time Synchronous Averaging and Synchronous Sampling 105 2.4.10 Hilbert Transform 106 2.4.11 Cross-spectrum 107 2.4.12 Coherence 109 2.4.13 Frequency-response (or Transfer) Function 110 2.4.14 Coherent Output Power 111 2.4.15 Convolution 112 2.4.16 Auto-correlation and Cross-correlation Functions 113 2.4.17 Maximum Length Sequence 115 Summary 117 References 117 2.3 2.4 2.5 3 Noise Generation 119 3.1 Introduction 119 3.1.1 Definitions 120 Aeroacoustics 122 3.2.1 Turbulence and Sound 3.2 122 Contents 3.3 3.4 3.5 3.6 3.2.2 The Effect of Solid Surfaces 124 3.2.3 The Effect of Moving Solid Surfaces 125 Aerodynamic Noise Generation on Wind Turbines 128 3.3.1 The Aerodynamic Environment of a Wind Turbine 3.3.2 Trailing-edge Noise 131 3.3.3 Separation-stall Noise 138 3.3.4 Tip Noise 139 3.3.5 Turbulence–Leading-edge Interaction Noise 141 3.3.6 Wind-shear Noise 144 3.3.7 Blade–Tower Interaction Noise 145 3.3.8 Thickness Noise 147 Aero-elasticity and Noise 148 Other Noise Sources 149 Summary and Outlook 151 References 152 128 4 Wind Turbine Sound Power Estimation 157 4.1 4.2 Introduction 157 Aerodynamic Noise Prediction 157 4.2.1 Types of Prediction Methods 157 Simple Models 158 Semi-empirical Methods (Class II Models) 159 4.4.1 Overall Framework 159 4.4.2 Aerodynamic Analysis 160 4.4.3 Boundary-layer Estimates 163 4.4.4 Airfoil Noise Models 164 4.4.5 Inflow Noise Model 166 4.4.6 Prediction of Total Sound Power 168 Computational Methods (Class III Models) 168 Estimations of Sound Power From Measurements 169 4.6.1 Instrumentation 170 4.6.2 Procedure 171 4.6.3 Data Analysis 172 4.6.4 Comments on Turbine Sound Power Measurements 174 4.6.5 Possible Improvements to Procedures for Measuring Turbine Sound Power Levels 175 Summary 177 References 177 4.3 4.4 4.5 4.6 4.7 5 Propagation of Noise and Vibration 180 5.1 5.2 Introduction 180 Principles Underpinning Noise Propagation Modelling 5.2.1 Spherical Spreading, Adiv 183 5.2.2 Atmospheric Absorption, Aatm 186 5.2.3 Ground Effect, Agr 187 5.2.4 Meteorological Effects, Amet 188 5.2.5 Barrier Effects, Abar 209 182 ix x Contents 5.3 5.4 5.5 5.6 5.7 5.8 5.9 5.2.6 Miscellaneous Propagation Effects, Amisc 209 5.2.7 Infrasound and Low-frequency Noise 210 5.2.8 Propagation Modelling Procedure 210 Simplest Noise Propagation Models 212 Danish Low-frequency Propagation Model 213 CONCAWE (1981) 214 5.5.1 Spherical Spreading, K1 214 5.5.2 Atmospheric Absorption, K2 214 5.5.3 Ground Effects, K3 215 5.5.4 Meteorological Effects, K4 215 5.5.5 Source-height Effects, K5 218 5.5.6 Barrier Attenuation, K6 218 5.5.7 In-plant Screening, K7 221 5.5.8 Vegetation Screening, K𝑣 221 5.5.9 Limitations of the CONCAWE Model 221 ISO9613-2 (1996) Noise Propagation Model 223 5.6.1 Ground Effects, Agr 224 5.6.2 Barrier Attenuation, Abar 225 5.6.3 Vegetation Screening, Af 227 5.6.4 Effect of Reflections other than Ground Reflections 228 5.6.5 Recommended Adjustments to the ISO9613-2 Model for Wind Farm Noise 228 5.6.6 Limitations of the ISO9613-2 Model 230 NMPB-2008 Noise Propagation Model 231 5.7.1 Ground, Barrier and Terrain Excess Attenuation, Agr+bar 232 5.7.2 Reflections from Vertical Surfaces 241 5.7.3 Limitations of the NMPB-2008 Model 242 Nord2000 Noise Propagation Model 242 5.8.1 Combination of Sound Rays from the Same Source Arriving at the Receiver via Different Paths 244 5.8.2 Ground, Barrier and Terrain Excess Attenuation, Agr+bar 249 5.8.3 Multiple Ground Reflections 252 5.8.4 Excess Attenuation, Asc , due to a Ray Travelling Through a Scattering Zone 255 5.8.5 Excess Attenuation, Ar , due to Reflection from a Facade or Building 256 5.8.6 Limitations of the Nord2000 model 259 Harmonoise (2002) Noise Propagation Engineering Model 260 5.9.1 Combination of Sound Rays from the Same Source Arriving at the Receiver via Different Paths (for Calculating Agr+bar ) 263 5.9.2 Coordinate Transformation for the Ground Profile 264 5.9.3 Ground, Barrier and Terrain Excess Attenuation, Agr+bar 266 5.9.4 Excess Attenuation due to Scattering 266 5.9.5 Excess Attenuation, Ar , due to Reflection from a Facade or Building 267 5.9.6 Limitations of the Harmonoise Model 268 Contents 5.10 5.11 5.12 5.13 5.14 5.15 Required Input Data for the Various Propagation Models 5.10.1 CONCAWE 269 5.10.2 ISO9613-2 269 5.10.3 NMPB-2008 270 5.10.4 Nord2000 271 5.10.5 Harmonoise 271 Offshore Wind Farm Propagation Models 272 Propagation Model Prediction Uncertainty 272 Outside versus Inside Noise at Residences 276 Vibration Propagation 280 5.14.1 Vibration Generation 281 5.14.2 Vibration Propagation 281 5.14.3 Vibration Detection 282 Summary 283 References 285 269 6 Measurement 289 6.1 6.2 Introduction 289 Measurement of Environmental Noise Near Wind Farms 290 6.2.1 Instrumentation 291 6.2.2 Effects of Wind 300 6.2.3 Wind Screens for Microphones 301 6.2.4 Microphone Height 307 6.2.5 Ambient or Background Noise Assessment 307 6.2.6 A- and C-weighted Levels 314 6.2.7 Infrasound and Low-frequency Noise 317 6.2.8 Indoor Measurements 322 6.2.9 Outdoor-to-indoor Noise Reduction 324 6.2.10 Amplitude Modulation and Variation 328 6.2.11 Psychoacoustic Descriptors 349 6.2.12 Tonality 351 6.2.13 Additional Turbine Noise Analysis Techniques 363 6.2.14 Compliance Testing 365 6.2.15 Beamforming for Source Localisation on Full-scale Wind Turbines 386 6.2.16 Measurement Uncertainty 387 Vibration 393 6.3.1 Instrumentation 394 6.3.2 Measurement 394 6.3.3 Analysis 395 Wind, Wind Shear and Turbulence 395 6.4.1 Instrumentation 395 6.4.2 Measurement 399 6.4.3 Analysis 401 Reporting on Noise, Vibration and Meteorological Conditions 405 Wind Tunnel Testing 408 6.6.1 Wind Tunnel Techniques 409 6.3 6.4 6.5 6.6 xi xii Contents 6.7 6.6.2 Noise Measurements in Wind Tunnels 413 6.6.3 Review of some Recent Measurements 422 Conclusions 425 References 425 7 Effects of Wind Farm Noise and Vibration on People 436 7.1 7.2 Introduction 436 Annoyance and Adverse Health Effects 441 7.2.1 Amplitude Modulation, Amplitude Variation and Beating 453 Hearing Mechanism 455 7.3.1 External Ear 455 7.3.2 Middle Ear 455 7.3.3 Inner Ear 457 7.3.4 Frequency Response of the Human Ear 459 Reproduction of Wind Farm Noise for Adverse Effects Studies 465 Vibration Effects 467 Nocebo Effect 467 Summary and Conclusion 468 References 470 7.3 7.4 7.5 7.6 7.7 8 Wind Farm Noise Control 476 8.1 8.2 Introduction 476 Noise Control by Turbine Design Modification 477 8.2.1 Optimisation of Blade Design 478 8.2.2 Trailing-edge Treatments 479 8.2.3 Blade-pitch Control 481 8.2.4 Phase Control 483 8.2.5 Control of Noise Resulting from Aeroacoustic Excitation of the Blades 485 8.2.6 Control of Noise Resulting from Mechanical Excitation of the Gearbox, Blades and Tower 486 Optimisation of Turbine Layout 487 Options for Noise Control at the Residences 488 8.4.1 Active Noise Control 488 8.4.2 Masking 492 Administrative Controls 492 Summary 493 References 493 8.3 8.4 8.5 8.6 9 9.1 9.2 9.3 9.4 9.5 496 Introduction 496 Further Investigation of the Effects of Wind Farm Noise on People 497 Improvements to Regulations and Guidelines 499 Propagation Model Improvements 504 Identification and Amelioration of the Problem Noise Sources on Wind Turbines 504 Recommendations for Future Research Contents 9.6 9.5.1 Identification of Noise Sources 504 9.5.2 Amelioration of Noise Sources 505 Reducing Low-frequency Noise Levels in Residences 506 References 506 A Basic Mathematics 507 A.1 A.2 A.3 A.4 Introduction 507 Logarithms 507 Complex Numbers 508 Exponential Function 508 B The BPM model 509 B.1 B.2 B.3 Boundary-layer Parameters 509 Turbulent Trailing-edge Noise Model 511 Blunt Trailing-edge Noise Model 513 Reference 515 C Ground Reflection Coefficient Calculations C.1 C.2 C.3 C.4 C.5 C.6 Introduction 516 Flow Resistivity 517 Characteristic Impedance 518 Plane-wave Reflection Coefficient 520 Spherical-wave Reflection Coefficient 521 Incoherent Reflection Coefficient 524 References 525 D Calculation of Ray Path Distances and Propagation Times for the Nord2000 Model 526 D.1 D.2 D.3 Introduction 526 Equivalent Linear Atmospheric Vertical Sound-speed Profile 527 Calculation of Ray Path Lengths and Propagation Times 529 D.3.1 Direct Ray 529 D.3.2 Reflected Ray 531 References 532 E Calculation of Terrain Parameters for the Nord2000 Sound Propagation Model 534 E.1 E.2 E.3 E.4 Introduction 534 Terrain Effects 534 Approximating Terrain Profiles by Straight-line Segments 539 Calculation of the Excess Attenuation due to the Ground Effect for Relatively Flat Terrain with no Diffraction Edges 540 Calculation of the Excess Attenuation due to the Ground Effect for Relatively Flat Terrain with a Variable Impedance Surface and no Diffraction Edges 541 Calculation of the Excess Attenuation due to the Ground Effect for Valley-shaped Terrain 543 E.5 E.6 516 xiii xiv Contents E.7 E.8 E.9 Identification of the Two Most Efficient Diffraction Edges 544 Calculation of the Sound Pressure at the Receiver for each Diffracted Path in Hilly Terrain 547 E.8.1 Diffraction over a Single Finite-impedance Wedge-shaped Screen 547 E.8.2 Diffraction over a Finite-impedance Thick screen with Two Diffraction Edges 550 E.8.3 Diffraction over Two Finite-impedance Wedges 554 Calculation of the Combined Ground and Barrier Excess-attenuation Effects 556 E.9.1 Terrain Involving a Single Diffraction Wedge 557 E.9.2 Terrain involving a Double Diffraction Wedge 561 E.9.3 Terrain involving Two Single Diffraction Wedges 561 References 563 F Calculation of Fresnel Zone Sizes and Weights 564 F.1 F.2 F.3 Introduction 564 Fresnel Zone for Reflection from Flat Ground 564 Fresnel Weights for Reflection from a Concave or Transition Ground Segment 567 Fresnel Weights for Reflection from a Convex Ground Segment 570 Reference 571 F.4 G Calculation of Diffraction and Ground Effects for the Harmonoise Model 572 G.1 G.2 G.3 Introduction 572 Diffraction Effect, ΔLD 574 Ground Effect 577 G.3.1 Concave Model 579 G.3.2 Transition Model 582 Fresnel Zone for Reflection from a Ground Segment 584 References 587 G.4 H Active Noise-control System Algorithms 588 H.1 H.2 H.3 Introduction 588 Single-input, Single-output (SISO) Weight Update Algorithm 588 Multiple-input, Multiple-output Weight Update Algorithm 590 References 592 Index 593 xv Wiley Series in Acoustics, Noise and Vibration This book series will embrace a wide spectrum of acoustics, noise and vibration topics from theoretical foundations to real world applications. Individual volumes will range from specialist works of science to advanced undergraduate and graduate student texts. Books in the series will review scientific principles of acoustics, describe special research studies and discuss solutions for noise and vibration problems in communities, industry and transportation. The first books in the series include those on Biomedical Ultrasound; Effects of Sound on People, Engineering Acoustics, Noise and Vibration Control, Environmental Noise Management; Sound Intensity and Windfarm Noise. Books on a wide variety of related topics. The books I edited for Wiley, the Encyclopedia of Acoustics (1997), the Handbook of Acoustics (1998) and the Handbook of Noise and Vibration Control (2007) included over 400 chapters written by different authors. Each author had to restrict their chapter length on their special topics to no more than about 10 pages. The books in the current series will allow authors to provide much more in-depth coverage of their topic. The series will be of interest to senior undergraduate and graduate students, consultants, and researchers in acoustics, noise and vibration and in particular those involved in engineering and scientific fields, including, aerospace, automotive, biomedical, civil/structural, electrical, environmental, industrial, materials, naval architecture and mechanical systems. In addition the books will be of interest to practitioners and researchers in fields such as audiology, architecture, the environment, physics, signal processing and speech. Malcolm J. Crocker Series Editor xvii Preface Wind farm noise has polarised communities and is featured on numerous web sites that either dismiss its effects on people as a nocebo effect or as something in their imagination. There are just as many other web sites that claim wind farm noise has led to serious medical problems in some people and that infrasound generated by wind farms can have far-reaching consequences for the health of people who are exposed. These web sites can be found easily by typing ‘wind farm noise’ into any internet search engine. Our intention when writing this book has been to cover all aspects of wind farm noise, including how it is generated, how it propagates, how it is assessed, how it is regulated and what effects it has on people living in the vicinity of wind turbines. Where aspects of wind farm noise are controversial, we have presented what we believe to be an unbiased assessment of the facts. None of the three authors have ever worked for the wind farm industry nor have they been members of any anti-wind-farm organisation. Only the first author has appeared as an expert witness, in a 2010 court proceedings concerned with a wind farm development. This was his only involvement in court proceedings and it was in the capacity of being asked to critique a report prepared by an acoustical consultant for a wind farm operator. The first two authors have been chief investigators on a number of research projects, funded by the Australian Research Council, on aerodynamic noise generation and the impact of wind farm noise on rural communities. The first author has also spent over 40 years teaching, researching and consulting in acoustics and noise control. The second author has spent nearly 20 years working in the area of aerospace engineering, with a strong focus on aeroacoustics: the science of how objects like rotor blades create sound. Following completion of a PhD in fluid mechanics, the third author has spend the past four years measuring and analysing wind farm noise. Wind farm noise is a very controversial subject, in that it has been used as a reason for delaying many wind farm projects that together are worth billions of dollars. Most court cases find in favour of the wind farm developer and very few wind farms are prevented from being constructed as a result of court proceedings based on excessive noise, although sometimes the turbine layout has had to be modified to minimise noise impacts on the surrounding communities. Nevertheless, even after wind farms have been constructed, many people complain of the noise keeping them awake at night and causing them to feel ill. In spite of the many reported cases of adverse effects of wind farm noise on people, wind farm proponents insist that wind farm noise is so low in level that it could not possibly be a problem. They often imply that affected people must be developing symptoms as a result of feelings of jealousy over payments received by wind turbine xviii Preface hosts or as a result of anti-wind-farm publicity telling them that wind farms produce such symptoms. Although we are neither pro- nor anti-wind-farm campaigners, we do believe that some people in the vicinity of some wind farms are badly affected by the noise and that further research into this phenomenon is absolutely essential. We hope that you the reader find the material in this book useful and, where it strays into areas that are controversial, that you find that we have achieved our aim of presenting a balanced point of view. Colin Hansen Con Doolan Kristy Hansen Adelaide, Australia 1 1 Wind Energy and Noise 1.1 Introduction Why write this book about noise generated by wind farms? Many people believe that wind farm noise is a non-issue and that people complain about it because they are unhappy with the lack of financial compensation they receive compared to their neighbours who are hosting the turbines. Other reasons that we often see on pro-wind-farm web sites are that the anti-wind-farm lobby has suggested a range of symptoms are caused by wind farms and that this suggestion has made some people living near wind farms develop these symptoms as a result: the ‘so-called’ nocebo effect. Although the authors of this book would consider themselves neither pro- nor anti-wind-farms, they have taken a sufficient number of their own measurements and spoken to a sufficient number of residents living in the vicinity of wind farms (including wind farm hosts) to appreciate that the character and level of wind farm noise is a problem for a significant number of people, even those who reside at distances of 3 km or more from the nearest turbine. Although one chapter in this book is concerned with the effects of wind farm noise on people, the main focus of this book is on how wind farm noise is generated and propagated, the characteristics of the noise arriving at residences in the vicinity of wind farms, and measurement procedures and instrumentation, as well as assessment criteria that are necessary for properly quantifying the noise. As many people living in the vicinity of wind farms report ‘feeling’ vibration when they lie down, vibration generation, propagation and measurement are also discussed in sections in Chapters 4, 5 and 6. To lay the foundation for the remaining chapters, the rest of this chapter is concerned with a description of how the wind industry has developed in various countries, followed by a brief history of noise studies (including a summary of noise levels generated by large wind turbines), a summary of some public inquiries and wind farm noise regulations, and finally a discussion of the current consensus on wind farm noise and its effects on people. It is not possible to usefully take part in the wind farm noise debate without having some understanding of acoustics. This is the reason for writing Chapter 2 to follow. First, basic concepts in acoustics necessary for understanding the legislation are discussed. This is followed by a discussion of the fundamentals of frequency analysis, which is an important tool for analysing wind farm noise. Chapter 2 concludes with a discussion of Wind Farm Noise: Measurement, Assessment and Control, First Edition. Colin H. Hansen, Con J. Doolan, Kristy L. Hansen. © 2017 John Wiley & Sons Ltd. Published 2017 by John Wiley & Sons Ltd. 2 Wind Farm Noise some advanced concepts of frequency analysis, an understanding of which is essential for practitioners wishing to undertake more advanced analyses of wind farm noise. Chapter 3 contains an overview of how wind turbines generate noise, while Chapter 4 is about estimating wind turbine sound power levels. Chapter 5 is concerned with using turbine sound power levels and sound propagation models to estimate noise levels in the community. Several propagation models are considered, beginning with the simplest and progressing to the more complex and supposedly more accurate models. Chapter 6 is devoted to a detailed description of procedures and instrumentation for the measurement of wind farm noise and vibration, and includes a discussion of potential errors associated with such measurements. The chapter also includes a discussion on wind tunnel measurements for testing turbine models. Chapter 7 is about the effects of wind farm noise on people, Chapter 8 contains a discussion of various options that can reduce wind turbine noise, both outside of and inside residences, and Chapter 9 contains some suggestions of where we should be heading in terms of wind farm noise research and the reduction of its effects on people. 1.2 Development of the Wind Energy Industry 1.2.1 Early Development Prior to 2000 Mankind has harvested energy from the wind for over a thousand years. The first device designed for this purpose was a vertical-axis, sail-type windmill developed in Persia between 500 and 900 AD. This design appears to have been inspired by boats that used their sails to harness the wind for propulsion. Windmills have been primarily used for water pumping and grain grinding, with the mechanical power developed in the rotating shaft used directly to drive a pump or turn a grindstone. Wind turbines differ from windmills in that they convert the mechanical power into electrical power through use of a generator. They also have a smaller number of blades, since windmills require high torque at low rotor speeds (Manwell et al. 2009); for optimal electrical power generation higher rotor speeds and thus fewer blades are desirable. This is because high rotor speeds result in increased loading and reducing the number of blades reduces stresses on the rotor (Manwell et al. 2009). Another factor to consider is that wind turbine blades are very costly and therefore it is beneficial to minimise their number. The most common wind turbine configuration that is used today is a horizontal-axis wind turbine (HAWT) and this book will concentrate on aspects of noise associated with this particular design, with a focus on large, industrial-scale wind turbines. The major components of a HAWT are shown in Figure 1.1. The basic principle of operation is that wind causes the blades to rotate and the rotor drives a shaft that is connected, generally via a gearbox, to a generator, which converts the rotational energy into electrical energy. The power output and rotational speed of a HAWT can be controlled either by designing the blades such that they begin to stall at a certain wind speed (stall control) or by having a mechanism and control system that is able to vary the blade pitch (pitch control, which involves rotation of the blades about the blade axis as opposed to the rotor axis). In a pitch-controlled turbine, the controller will continually adjust the blade pitch to ensure that the power output is optimised for the wind speed being experienced by the blade. A pitch controlled machine can also be easily ‘turned off’ to protect the turbine when 1 Wind Energy and Noise LE TE Blade Hub Nacelle structure enclosing drive train Wind LE TE Tower Foundation Figure 1.1 Schematic of typical wind turbine: LE, leading edge; TE, trailing edge. the wind speed becomes too great. This is done by adjusting the pitch of the blades so that they no longer generate appreciable lift. A stall-controlled turbine blade is designed with some twist to ensure the blade stalls gradually along its length. The blade profile also has to be designed so that it stalls just as the wind speed becomes too high, thus reducing the lift force acting on the blade, which in turn limits the blade speed and power. An active stall-controlled turbine is similar to a pitch-controlled turbine in that the pitch is continually adjusted to optimise the power output. However, when the wind speed becomes too great, the stall-controlled turbine will rotate the blades so that they stall, as opposed to a pitch-controlled turbine, which rotates the blades in the opposite direction so that the lift is minimised. In some cases, turbines are also controlled using yaw control. This involves turning the rotor so the blades no longer face directly into the wind. However, this is only used on small turbines and is not relevant to the turbines that are the subject of this book. Development of large HAWTs for incorporation into electric utilities first began in the early 1930s with the construction of the Balaklava wind turbine in Russia, which was 30 m in diameter, two-bladed and rated to a power of 100 kW. This turbine 3 4 Wind Farm Noise operated for around two years and generated 200 MWh (Sektorov 1934). In the late 1930s, development of the first megawatt-scale wind turbine began in the USA in a collaborative project between an engineer named Palmer C. Putnam and the Smith company, which was experienced in the construction of hydroelectric turbines and electrical power equipment. The Smith–Putnam HAWT consisted of a two-bladed rotor of diameter 53.3 m, mounted on a truss-type tower at a rotor-axis height of 33.5 m (Putnam 1948). This wind turbine was rated at 1.25 MW and included a number of technological innovations such as blade-pitch control, flapping hinges on the blades to reduce dynamic loading on the shaft, and active yaw control (Spera 2009). Several weeks of continuous operation yielded excellent power production and it was demonstrated that the wind turbine was capable of being inserted into the grid. Unfortunately, development was discontinued in 1945 when a faulty blade spar separated at the repair weld and there were insufficient funds to continue the project. Over the next 25 years, development proceeded at a modest rate, taking place predominantly in Western Europe, where there was a temporary post-war shortage of fossil fuels that led to increased energy prices. Two HAWT designs emerged from Denmark and Germany during this time, and these would form the basis of future wind turbine development in the 1970s. The 24-m diameter, 200 kW Gedser Mill wind turbine was constructed in Denmark and was designed by Johannes Juul. The rotor consisted of three fixed-pitch blades that were connected with a support frame to improve structural integrity. This frame was removed in later years when the metal blades were replaced with fibreglass ones (Dodge 2006). The rotor was located upwind of the concrete tower and the design was notable for its simplicity, ruggedness and reliability. This wind turbine supplied AC power to the local utility from 1958 until 1967, achieving annual capacity factors of 20% in some years (Spera 2009). The annual capacity factor is defined as the ratio of the energy generated in one year to the amount that could be generated if the turbines operated continuously at their maximum power output. In 1967, a mechanical failure resulted in discontinued use of the wind turbine and the machine remained idle for the next 10 years (Auer 2013). Considerable research effort, with a focus on improved rotor technology, led to the development of the Hütter–Allgaier wind turbine in Germany in the early 1960s. With a diameter of 34 m and rated at 100 kW, it was technologically advanced for its time and included an important design feature of a bearing at the rotor hub that allowed the rotor to ‘teeter’, in order to minimise the dynamic loading that results from the changes in gyroscopic inertia about the tower axis that arise when the blades of a two-bladed rotor move between the horizontal and vertical positions. A teetering rotor is illustrated schematically in Figure 1.2, which shows the bearing that facilitates the teetering motion. Despite its technological proficiency, the Hütter–Allgaier wind turbine encountered flutter in its long, slender blades, which slowed research progress. Wind turbines were successfully connected to the grid in France in the period from 1958 to 1964 and the largest such turbine was called the Type Neyrpic, which was 35 m in diameter and rated at 1.1 MW. While this wind turbine demonstrated good performance, its operation was terminated abruptly when the turbine shaft broke. In the UK, a number of unique 100 kW wind turbine designs were conceived and built in the 1950s with the intention of local grid connection. These turbines operated successfully for a few years, but technical and environmental factors led to the cessation of operations by 1963. Many projects were discontinued during this 25-year period due

Author Colin H. Hansen, Con J. Doolan, and Kristy L. Hansen Isbn 9781118826065 File size 10.8MB Year 2017 Pages 624 Language English File format PDF Category Physics Book Description: FacebookTwitterGoogle+TumblrDiggMySpaceShare A comprehensive guide to wind farm noise prediction, measurement, assessment, control and effects on people Wind Farm Noise covers all aspects associated with the generation, measurement, propagation, regulation and adverse health effects of noise produced by large horizontal-axis wind turbines of the type used in wind farms. The book begins with a brief history of wind turbine development and the regulation of their noise at sensitive receivers. Also included is an introductory chapter on the fundamentals of acoustics relevant to wind turbine noise so that readers are well prepared for understanding later chapters on noise measurements, noise generation mechanisms, noise propagation modelling and the assessment of the noise at surrounding residences. Key features: Potential adverse health effects of wind farm noise are discussed in an objective way. Means for calculating the noise at residences due to a wind farm prior to construction are covered in detail along with uncertainty estimates. The effects of meteorological conditions and other influences, such as obstacles, ground cover and atmospheric absorption, on noise levels at residences are explained. Quantities that should be measured as well as how to best measure them in order to properly characterise wind farm noise are discussed in detail. Noise generation mechanisms and possible means for their control are discussed as well as aspects of wind farm noise that still require further research to be properly understood. The book provides comprehensive coverage of the topic, containing both introductory and advanced level material.     Download (10.8MB) Non-diffracting Waves Acoustic Absorbers and Diffusers, Third Edition: Theory, Design and Application Wind Energy Systems: Control Engineering Design Computational Techniques Of Rotor Dynamics With The Finite Element Method Aeroelastic Vibrations and Stability of Plates and Shells Load more posts

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