Resource Documents: Technology (122 items)
Documents presented here are not the product of nor are they necessarily endorsed by National Wind Watch. These resource documents are provided 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.
Reproducing wind farm infrasound for subjective testing – Just how accurate is the reproduced signal?
Author: Cooper, Steven
In response to investigation of residents’ complaints concerning the operation of wind turbines, independent acousticians have identified the presence of a discrete infrasound/low frequency signature associated with the operation of the turbine to be present when such turbines are operating.
The discrete signature of turbines when using narrowband analysis reveals peaks at the blade pass frequency (and harmonics of that frequency) to occur in the lower portion of the infrasound frequency band, generally below 10 Hz and a peak with sidebands around what may be the gearbox output shaft speed.
Attenuation of infrasound over distance occurs at a lower rate than that of normal sound, resulting in the discrete infrasound signature of turbines being recorded up to 7 km from wind farms, and in some situations even greater distances.
Infrasound measurements of the natural environment in rural areas free from the influence of wind turbines whilst revealing similar broadband levels of infrasound (for example using dBG or even 1/3 octaves) do not experience a discrete periodic pattern similar to that associated with rotating blades on wind turbines when assessed in narrow bands.
In seeking to assess the audible characteristics of wind turbine noise, being different to that of general traffic or environmental noise, laboratory studies have sought to use speakers to generate or to reproduce recorded signals for test subjects in a controlled environment. …
As the impact of the turbine’s inaudible infrasound on people has not been studied in controlled studies, of critical importance in the laboratory assessment of wind turbine “noise” is the question as to whether the source signals generated in the laboratory are full spectrum and reproduce the original signal (that includes by narrowband analysis infrasound). …
Tachibana [Yokoyama S, Kobayashi T, Sakamoto S & Tachibana H, “Subjective experiments on the auditory impression of the amplitude modulation sound contained in wind turbine noise”, International Meeting on Wind Turbine Noise, Glasgow 2015] used a set of reverberation chambers to evaluate full spectrum sound of wind turbines. However, the primary issue presented in the paper was looking at the A-weighted level with different low pass filtering and modulation. Reference  did not examine infrasound specifically but concluded that frequency components below 25 Hz are not audible which is to be expected for the levels that were tested. As a side issue to the investigation of the A-weighted levels and audibility of the modulation, the audible modulation effects were identified as associated with low frequency.
Walker [Walker B & Celano J, “Progress report on synthesis of wind turbine noise and infrasound”, 6th International Meeting on Wind Turbine Noise, Glasgow 2015] provided results of generating infrasound signals synthesised from narrow band Leq analysis to find no impact. No frequency response was provided to define the output of the synthesised infrasound signal generated by a speaker. There is an assumption the system equalisation curve resulted in a flat spectrum.
Walker [Hansen K, Walker B, Zajamsek B & Hansen C, “Perception and annoyance of low frequency noise versus infrasound in the context of wind turbine noise”, International Meeting on Wind Turbine Noise, Glasgow 2015] started with external wind farm noise samples from the Waterloo wind farm that were then synthesised from the narrow band frequency spectrum to provide the source signal.
Tonin [Tonin R & Brett J, “Response to simulated wind farm infrasound including effect of expectation”, International Meeting on Wind Turbine Noise, Glasgow 2015] used a synthesised infrasound signal applied to a pnuematic driver connected to modified hearing protectors.
Crichton [Crichton F, Dodd G, Schmid G, Gamble G & Petrie K, “Can expectations produce symptoms from infrasound associated with wind turbines?”, Health Psychology, 33(4), 360-364 (2014); Crichton F, Dodd G, Schmid G, Gamble G, Cundy T & Petrie K, “The power of positive and negative expectations to influence reported symptoms and mood during exposure to wind farm sound?”, Health Psychology, American Psychological Association 2013] used single infrasound tones inserted into broad band noise for an assessment of “wind turbine infrasound”. …
Issues of concern with the use of simulated “infrasound” are:
- Whether the synthesised signal (obtained from adding sine waves) reproduces the actual time signal that occurs in the field.
- “Infrasound” applied as single tones and then attributed as being the signal generated by wind farms.
- Testing of synthesised signal and claiming the results apply to wind farms.
- Accurately reproducing the Wave file signal by the use of speakers.
Steven Cooper, The Acoustic Group, Lilyfield, NSW, Australia
171st Meeting of the Acoustical Society of America, Salt Lake City, Utah, 23-27 May 2016. Noise: Paper 4aNS10
Download original document: “Reproducing wind farm infrasound for subjective testing – Just how accurate is the reproduced signal?”
Author: Palmer, William
Numerous papers, including some by this author, have identified what are dismissed with disdain as “anecdotal reports” of adverse impacts that occurred with the start up of wind turbines in the environment of those impacted. However, there is a solid basis for presenting such lists. It mirrors the approach taken by most medical doctors when a patient first presents himself or herself with a new adverse health complaint. Taking a patient “history” is the way most doctors begin. Similarly, engineers and problem solvers often begin to address a new problem by looking for changes that have occurred. Yet, some maintain there is no proof that the start up of the turbines was the change that caused the impact, even though the conditions diminish when the person vacates the area, and recur when the person returns. They may attribute it to the stress self-generated by refusing to accept a change. Ignoring those suffering will not result in solving the problem predicted by Kryter of people making real-life behavioral changes. The rigorous method established in this paper permits measuring the physical emissions (noise) from wind turbines, and confirming some aspects of the quality of the noise that are identified as problematic to demonstrate evidence of the cause for the suffering.
William K. G. Palmer, P.Eng., TRI-LEA-EM
7th International Conference on Wind Turbine Noise – Rotterdam – 2nd to 5th May 2017
Download original document: “A Rigorous Method of Addressing Wind Turbine Noise”
Author: Xcel Energy
Download video (52-MB MP4)
- 100 Vestas V100 2-MW turbines
- Nearly 25,000 acres (101 km²)
- 22 miles of access roads
- Substation transformer: 262,000 pounds
- Substation increases voltage for transmission lines
- 17.1-mile 115-kV overhead transmission line from collection substation to interconnect substation
- More than 150 miles of underground cable in 50 miles of trench
- Tower base (platform) excavation depth: 9 feet
- 360 cubic yards of concrete, 28 tons of reinforcing steel
- Tower base (bottom third): 96,000 pounds, 128 anchor bolts
- Nacelle: 163,650 pounds
- Hub height: 262 feet
- Turbine blade: length 161 feet, weight 17,000 pounds
- Total height: 426 feet
- Blade diameter: 328 feet
- Blade sewep area: 1.94 acres
Author: Bel, G.; Connaughton, C.P.; Toots, M.; and Bandi, M.M.
Wind power fluctuations at the turbine and farm scales are generally not expected to be correlated over large distances. When power from distributed farms feeds the electrical grid, fluctuations from various farms are expected to smooth out. Using data from the Irish grid as a representative example, we analyze wind power fluctuations entering an electrical grid. We find that not only are grid-scale fluctuations temporally correlated up to a day, but they possess a self-similar structure—a signature of long-range correlations in atmospheric turbulence affecting wind power. Using the statistical structure of temporal correlations in fluctuations for generated and forecast power time series, we quantify two types of forecast error: a timescale error (eτ) that quantifies deviations between the high frequency components of the forecast and generated time series, and a scaling error (eζ) that quantifies the degree to which the models fail to predict temporal correlations in the fluctuations for generated power. With no a priori knowledge of the forecast models, we suggest a simple memory kernel that reduces both the timescale error (eτ) and the scaling error (eζ).
Department of Solar Energy and Environmental Physics, Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev, Sede Boqer Campus, Israel
C P Connaughton
Centre for Complexity Science, University of Warwick, Coventry, U.K.
M Toots and M M Bandi
Collective Interactions Unit, Okinawa Institute of Science and Technology Onna, Okinawa, Japan
Published 1 February 2016 • New Journal of Physics, Volume 18, February 2016
Download original document: “Grid-scale fluctuations and forecast error in wind power”