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Resource Documents: Technology (142 items)


Also see NWW "technology" and "size" FAQs

Unless indicated otherwise, documents presented here are not the product of nor are they necessarily endorsed by National Wind Watch. These resource documents are shared here to assist anyone wishing to research the issue of industrial wind power and the impacts of its development. The information should be evaluated by each reader to come to their own conclusions about the many areas of debate. • The copyrights reside with the sources indicated. As part of its noncommercial effort to present the environmental, social, scientific, and economic issues of large-scale wind power development to a global audience seeking such information, National Wind Watch endeavors to observe “fair use” as provided for in section 107 of U.S. Copyright Law and similar “fair dealing” provisions of the copyright laws of other nations.

Date added:  September 15, 2019
Denmark, Europe, Germany, Italy, Netherlands, Noise, Regulations, TechnologyPrint storyE-mail story

Implementation of the issue of noise from wind turbines at low frequencies

Author:  Marini, Martino; et al.

The enduring energy scenario leads to further promote the development of the exploitation of renewable energy sources. Recent European standards have been defining a path to reach in 2050 a level of decarbonization lower of 80% compared to 1990. Wind farms have been growing quickly for [the] last decade with individual wind turbines getting larger and larger. In addition to the benefits of containing greenhouse gas emissions and restraining the use of depletable resources, drawbacks have also appeared due to noise generation from wind turbines and adverse reaction of some nearby residents. The noise generated by wind turbines has a broad spectrum character but the low frequency noise causes special problems. It is a fact that in different European countries special laws have been adopted to impose noise limits and evaluation methods for the assessment of environmental low frequency noise from this kind of sound source. Other countries are still lacking specific rules but in the authorization procedure such analysis is required by environmental control agencies. The purpose of this study consists of comparing the assessment procedures currently used in different European countries for the prediction of low frequency noise from wind turbines and its propagation. The comparison of procedures gives a chance to put forward progressions in low frequency noise emission and reception.

Martino MARINI, DADU University of Sassari, Italy
Costantino Carlo MASTINO, Roberto BACCOLI, Andrea FRATTOLILLO, DICAAR University of Cagliari, Italy
Antonino DI BELLA5, DII University of Padova, Italy

Proceedings of the 23rd International Congress on Acoustics, 9–13 September 2019, Aachen, Germany: pages 1441–1446

Download original document: “Implementation of the issue of noise from wind turbines at low frequencies

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Date added:  September 2, 2019
Noise, TechnologyPrint storyE-mail story

Effect of unsteady flow on wind turbine wake development and noise generation

Author:  Sedaghatizadeh, Nima

«The results of this study show that underlying mechanism associated with the perceived noise in the far-field of the turbine blades is amplitude modulation due to partial stall on the blades or interaction of the blades with incoming turbulent structures. This is in contrast with the common belief of trailing edge noise to be the dominant source for the perceived noise and its amplitude modulation due to rotation of the blades. Moreover, it is observed that the majority of the locations in which the noise from whole turbines is perceived by the community, are in close proximity of the wake region. … Results revealed that, the highest noise level in the vicinity of a wind turbine corresponds to blade pass frequency and is due to amplitude modulation of the trailing edge noise caused by the rotation of the blade, as well as blade tower interaction. Results also showed that the emitted noise is refracted due to the wind shear in atmospheric boundary layer, as well as the wake and associated turbulent structures. The [computational fluid dynamics] outcomes showed that the wake breakdown occurs at a distance of 12 diameters downstream of the turbine with a strong downwash due to longitudinal vortices. Contours of sound pressure level at the breakdown location of the wake of the wind turbine showed refraction and modulation of the sound at this location. Results also revealed refraction of the noise towards the ground and wider areas due to existence of the longitudinal vortices.»

Schematic diagram of the typical vortex system downstream of a wind turbine

Nima Sedaghatizadeh
School of Mechanical Engineering, University of Adelaide, Australia
Thesis submitted in fulfilment of the requirements for the degree of Ph.D. in Mechanical Engineering

Download original document: “The effect of unsteady flow on wind turbine wake development and noise generation

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Date added:  June 21, 2019
Noise, TechnologyPrint storyE-mail story

Investigation of a microphone height correction for long-range wind farm noise measurements

Author:  Hansen, Kristy; Zajamšek, Branko; and Hansen, Colin

In the measurement of wind farm noise, it is standard practice to mount outdoor microphones at a height of 1.5 m. On the other hand, measurements at this height can be affected by wind-induced noise, which has the potential to mask the noise of interest, particularly at low and infrasonic frequencies. Therefore, to minimise wind-induced noise, it is advantageous to measure on or below the ground, where the wind speed is close to zero. However, results from measurements taken at any height other than 1.5 m must be interpreted with caution, due to different interference effects between direct and ground-reflected waves at each location. This investigation explores the feasibility of using a prediction model based on Nord2000 algorithms to correct the 1/3-octave sound pressure level measured at ground level to obtain a representative value for a height of 1.5 m. The model takes into account phase changes due to the difference in travel-time for the direct and reflected rays and finite ground impedance, multiple source contributions and incoherence due to turbulence. The focus is on propagation distances greater than 2 km, where limited validation of existing propagation models has been attempted previously. Comparison is made between the model and measurement results obtained at four locations near a wind farm, where microphones were mounted at a height of 1.5 m and at ground level. A lack of agreement between measurements and the model indicates that the efficient and practical correction method considered here is not feasible for long-range wind farm measurements. Thus, it is recommended that wind farm noise is measured at both 1.5 m (for mid- to high-frequency noise) and at ground level (for low-frequency noise, which is more affected by wind).

Kristy L. Hansen, Branko Zajamšek, College of Science and Engineering, Flinders University, Tonsley, Australia
Colin H. Hansen, School of Mechanical Engineering, University of Adelaide, Adelaide, Australia

Applied Acoustics
Volume 155, 1 December 2019, Pages 97-110
doi: 10.1016/j.apacoust.2019.05.015

Investigation of a microphone height correction for long-range wind farm noise measurements

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Date added:  June 19, 2019
Noise, TechnologyPrint storyE-mail story

Experimental and numerical investigation of blade–tower interaction noise

Author:  Zajamšek, Branko; et al.

This paper describes the generation of blade–tower interaction (BTI) noise from upwind turbines and pylon-mounted fans using a combination of experimental and numerical means. An experimental rotor-rig was used in an anechoic chamber to obtain BTI acoustic data under controlled conditions. A computational model, based on the solution of the unsteady Reynolds Averaged Navier Stokes (URANS) equations and Curle’s acoustic analogy, was used to describe the generation of fan and simplistic model of wind turbine BTI noise by the rotor-rig. For both the fan and model wind turbine case, the tower was found to be a more significant source of BTI noise than rotor blades. The acoustic waveforms for both turbine and fan are similar; however, in the case of the turbine, the blade contribution reinforces that from the tower, while in the case of a fan, there is some cancellation between the tower source and the blade source. This behavior can be explained by the unsteady aerodynamics occurring during BTI.

Branko Zajamsek, Kristy L. Hansen, College of Science and Engineering, Flinders University, Adelaide, Australia
Yendrew Yauwenas, Con J.Doolan, Victoria Timchenko, John Reizes, School of Mechanical and Manufacturing Engineering, University of New South Wales, Sydney, Australia
Colin H. Hansen, School of Mechanical Engineering, University of Adelaide, Adelaide, Australia

Journal of Sound and Vibration
Volume 443, 17 March 2019, Pages 362-375
doi: 10.1016/j.jsv.2018.11.048

Download original document: “Experimental and numerical investigation of blade–tower interaction noise

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