Wind Turbine Noise

Frontmatter

1. Introduction

Abstract

In 1991, the world-wide electricity production amounted to 12030·10⁹ kWh, being 20450·10⁹ kWh in 2010 as projected by the IEA [180]. The resources of current energy sources are limited, i.e. uranium will be available until 2050–2100, coal until 2110–2190, gas until 2025–2050, and oil until 2020–2030 [180]. Together with the need for reducing air pollution, this leads to a need for increasing contribution of the renewable energy sources.

Siegfried Wagner, Rainer Bareiß, Gianfranco Guidati

2. Noise and its Effects

Abstract

Sound can be generated by a multitude of mechanisms. The sound emitted by a vibrating surface, e.g. a bell or a loudspeaker, is well-known to most people. Another mechanism is the periodic injection of air in the case of a siren. Several mechanisms are involved in the production of aerodynamic noise from wind turbines which is the topic of this book. Chapters 3–5 are dedicated to this subject.

Siegfried Wagner, Rainer Bareiß, Gianfranco Guidati

3. Introduction to Aeroacoustics

Abstract

One aim of this book is to give suggestions how aerodynamic noise from wind turbines can be reduced in order to increase the public’s acceptance of this energy source. An important prerequisite to find solutions that go beyond state-of-the-art knowledge is to understand the mechanisms of aerodynamic sound generation. Therefore, this chapter gives an introduction to some basic equations and concepts of aeroacoustics.

Siegfried Wagner, Rainer Bareiß, Gianfranco Guidati

4. Noise Mechanisms of Wind Turbines

Abstract

This chapter describes the principal noise mechanisms related to wind turbines. After a general discussion of all wind turbine noise sources — including machinery noise and aerodynamic noise — the mechanisms of each aerodynamic noise source are dealt with in more detail. Thus, the spectral properties, their relative significances compared to other noise mechanisms, the key parameters affecting them, and possible means for noise reduction are addressed. The topic of noise reduction is discussed in Chapter 8.

Siegfried Wagner, Rainer Bareiß, Gianfranco Guidati

5. Noise Prediction

Abstract

This chapter deals with the prediction of the noise produced by a given turbine under prescribed operating conditions. Beginning with simple rules of thumb for the overall sound pressure level at a given location, models for noise prediction of the whole frequency range are presented. Typical results obtained with the models illustrate the range of application and limitations of state-of-the-art noise prediction. The chapter concludes with developments required and recommendations for improved noise prediction codes.

Siegfried Wagner, Rainer Bareiß, Gianfranco Guidati

6. Noise Propagation

Abstract

Chapters 4 and 5 describe noise generation of wind turbines and its prediction, and Chapter 7 deals with noise and flow measurement. This chapter covers noise propagation.

Siegfried Wagner, Rainer Bareiß, Gianfranco Guidati

7. Measurement of Noise and Flow Field

Abstract

Only recently, wind tunnels have been accepted as facilities for investigating wind turbine noise, although many American airframe noise studies (e.g. [26], [28], [62], [101], [172], [189]) had proved that a wind tunnel set-up offers unique capabilities for airfoil self-noise studies.

Siegfried Wagner, Rainer Bareiß, Gianfranco Guidati

8. Noise Reduction

Abstract

Chapter 5 has described the approaches for predicting the noise emission due to the different noise mechanisms introduced in Chapter 4. It became clear that current prediction codes can give an overall estimate of the noise of a blade section or a whole wind turbine, but often fail to predict correct spectral shapes. However, since the mechanisms of noise generation are partly well understood there will be a possibility of deducing ways to reduce the noise even if it is not possible to compute it correctly. Based on theoretical findings and extensive experimental work, this chapter shows how a noise reduction may be accomplished.

Siegfried Wagner, Rainer Bareiß, Gianfranco Guidati

9. Future Work

Abstract

This chapter contains a summary of ideas and recommendations for future work in the field of wind turbine noise. It is neither complete nor meant as giving the ‘final answer’ to all questions. However, during reviewing the work performed in JOULE II, it became clear, that there are three important fields for future research on wind turbine noise, namely modeling, reduction, and experimental work.

Siegfried Wagner, Rainer Bareiß, Gianfranco Guidati

10. References

Siegfried Wagner, Rainer Bareiß, Gianfranco Guidati

Backmatter