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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:  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

Abstract:
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 20, 2019
Contracts, IowaPrint storyE-mail story

Agreement Regarding Easements

Author:  Diamond Trail Wind Energy

Purpose of Easement. The easements and grant of rents, royalties, credits and profits created by this Agreement (collectively, the “Easement”) are solely and exclusively for wind energy purposes, and not for any other purpose, and Grantee shall have the exclusive right to use the Property for wind energy purposes and to derive all profits therefrom. For purposes of this Agreement, wind energy purposes means converting wind energy into electrical energy, and collecting and transmitting the electrical energy so converted, together with any and all activities related thereto (“Development Activities”), including, without limitation, (a) determining the feasibility of wind energy conversion and other power generation on the Property, including studies of wind speed, wind direction and other meteorological data, and extracting soil samples; (b) constructing, laying down, installing, using, replacing, relocating and removing from time to time, and maintaining and operating, wind turbines, overhead and underground electrical and communications lines (“Collection/Transmission Facilities”), electric transformers, energy storage facilities, telecommunications equipment, power generation facilities to be operated in conjunction with large wind turbine installations, roads, meteorological towers and wind measurement equipment, and related facilities and equipment (collectively “Wind power Facilities”) on the Property; (c) overhanging rotors of wind turbines installed on adjacent land; (d) capturing, using, and converting unobstructed wind resources over and across the Property; (e) wind turbine operations, including electromagnetic, audio, flicker, visual, view, light, noise, vibration, air turbulence, wake, electrical, radio interference, shadow and other effects attributable to wind turbines; and (f) undertaking any other activities, whether accomplished by Grantee or a third party authorized by Grantee, that Grantee reasonably determines are necessary, useful or appropriate to accomplish any of the foregoing, including without limitation, exercising the right of ingress to and egress from Windpower Facilities (whether located on the Property, on adjacent property or elsewhere) over and across the Property by means of roads and lanes thereon if existing, or otherwise by such route or routes as Grantee may construct from time to time (“Access Rights”).

Project. The Parties acknowledge and agree that the Property, together with the other property included in the Project, will be interrelated and integrated in the operation of one or more larger wind energy conversion projects. The easements and other rights granted herein are an integral part of each Project. So long as any Windpower Facilities in a Project are in commercial operation, the Property shall be deemed to be in commercial operation, notwithstanding whether Windpower Facilities are actually installed upon the Property. Grantee may determine whether any particular group of Windpower Facilities constitutes a single Project or multiple Projects for purposes of this Agreement, and in the case of multiple Projects, which portion of the Property shall be included within each Project.

Download original document: “Agreement Regarding Easements – Diamond Trail Wind Energy

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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.

Abstract:
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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Date added:  June 18, 2019
Australia, NoisePrint storyE-mail story

Prevalence of wind farm amplitude modulation at long-range residential locations

Author:  Hansen, Kristy; Nguyen, Phuc; Zajamšek, Branko; Catcheside, Peter; and Hansen, Colin

Abstract:
The presence of amplitude modulation (AM) in wind farm noise has been shown to result in increased annoyance. Therefore, it is important to determine how often this characteristic is present at residential locations near a wind farm. This study investigates the prevalence and characteristics of wind farm AM at 9 different residences located near a South Australian wind farm that has been the subject of complaints from local residents. It is shown that an audible indoor low-frequency tone was amplitude modulated at the blade-pass frequency for 20% of the time up to a distance of 2.4 km. The audible AM occurred for a similar percentage of time between wind farm percentage power capacities of 40% and 85%, indicating that it is important that AM analysis is not restricted to high power output conditions only. Although the number of AM events is shown to reduce with distance, audible indoor AM still occurred for 16% of the time at a distance of 3.5 km. At distances of 7.6 and 8.8 km, audible AM was only detected on one occasion. At night-time, audible AM occurred indoors at residences located as far as 3.5 km from the wind farm for up to 22% of the time.

Kristy L. Hansen, Phuc Nguyen, College of Science and Engineering, Flinders University, Tonsley, Australia
Branko Zajamšek, Peter Catcheside, College of Medicine, Flinders University, Bedford Park, Australia
Colin H. Hansen, School of Mechanical Engineering, The University of Adelaide, Adelaide, Australia

Journal of Sound and Vibration
Volume 455, 1 September 2019, Pages 136-149
doi: 10.1016/j.jsv.2019.05.008

Download original document: “Prevalence of wind farm amplitude modulation at long-range residential locations

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