Resource Documents: Technology (127 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.
Author: Barlas, Emre; et al.
The unsteady nature of wind turbine noise is a major reason for annoyance. The variation of far-field sound pressure levels is not only caused by the continuous change in wind turbine noise source levels but also by the unsteady flow field and the ground characteristics between the turbine and receiver. To take these phenomena into account, a consistent numerical technique that models the sound propagation from the source to receiver is developed. Large eddy simulation with an actuator line technique is employed for the flow modelling and the corresponding flow fields are used to simulate sound generation and propagation. The local blade relative velocity, angle of attack, and turbulence characteristics are input to the sound generation model. Time-dependent blade locations and the velocity between the noise source and receiver are considered within a quasi-3D propagation model. Long-range noise propagation of a 5 MW wind turbine is investigated. Sound pressure level time series evaluated at the source time are studied for varying wind speeds, surface roughness, and ground impedances within a 2000 m radius from the turbine.
Emre Barlas, Wen Zhong Shen, and Kaya O. Dag
— Department of Wind Energy, Technical University of Denmark, Kongens Lyngby, Denmark
Wei Jun Zhu – School of Hydraulic, Energy and Power Engineering, Yangzhou University, Yangzhou, China
Patrick Moriarty – National Wind Technology Center, National Renewable Energy Laboratory, Boulder, Colorado, USA
The Journal of the Acoustical Society of America 2017 Nov;142(5):3297.
Download original document: “Consistent modelling of wind turbine noise propagation from source to receiver”
Author: Wind Energy Update
- O&M costs for wind power are double or triple the figures originally projected; they are particularly high in the U.S.
- There’s a −21% change in wind farm return on investment. This underperformance of wind assets is most likely attributable to both differences in power production and O&M costs over original estimates.
- $0.027/kWh, or €0.019/kWh, is the average values of O&M costs obtained from report surveys. This compares to early estimates by one of the world’s dominant turbine suppliers of $0.005/kWh.
- A significant amount of R&D is currently going into gearbox reliability. Many gearboxes, designed for a 20-year life, are failing after 6 to 8 years of operation.
- Data suggests that O&M challenges for wind turbines peaked in 2007/2008.
- At 2 cents/kWh, O&M costs are roughly equal to the federal production tax credit offered in the U.S. as a subsidy to make wind energy competitive.
- Engineers are still scratching their heads when it comes to gearboxes. Even though gearboxes are certified to operate for 20 years, none of them on today’s market lasts more than 8 years.
- 66% – the percentage of offshore O+M costs that are caused by unscheduled corrective maintenance
- 2-6 times higher – offshore wind turbines O+M costs compared with on-shore
- 10% – the loss in revenue due to the effect of spattered debris accumulation on the blade’s leading edge
- €100,000 to €300,000 per year – the costs of keeping offshore turbines online vs. an allocation of €45,000 per turbine for onshore wind
As part of our research into failure rates, costs and downtime on US Wind Farms, we have built a model which estimates lifetime costs of scheduled maintenance for a wind farm in the US. The input data used to build this data pack is a 210MW wind farm made up of 105 2MW turbines of 80 metres in height. The tables below show component risk factors, periodic maintenance costs, failure scenarios and supply chain factors [all costs USD]. CMS [complete monitoring system] options play an increasingly important role in both mean time to repair and the time between failures. As a result they have a large impact on costs. These are also taken into account. Finally the data pack provides major component lifetime O&M cost for the wind farm.
Scheduled maintenance cost—
Frequency per year: 2
Cost per action per turbine: $6,000
Reduced cost: $5,100
Lifetime cost per farm: $21,420,000
Component risk factors—
|Components||Replacement cost||Failure rate (%), failures per 100 parts by year 20||Total failures in 20 years (total farm)||Average downtime per failure, days||Average downtime losses per faiure||Total downtime losses for the rest of the||Labor cost per failure||Crane cost per failure|
Supply chain risk factors—
|Spare in stock / No spare||Distance to manufacturing facility (if no spare available)|
|Available / No spare||Lead time, days||Close / Medium / Remote||Time for transportation, days|
CMS factors (per turbine)—
|Capital Sensor Cost (including installation) per turbine||Annual cost (O&M) per turbine||Detectability||Efficiency|
|Monitoring type||Cost||Reduced cost (economies of scale)||Fixed cost||Reduced cost (economies of scale)|
|Lifetime maintenance cost for the farm||Lifetime maintenance cost assuming secondary damage||Lifetime maintenance and CMS operation cost for the farm||Monitoring type|
We have also looked at failure rates across different turbine technology types and designs. The graph below shows major component failure rates for all types of turbines in our dataset during the first ten years of operations. Different failure modes have different repair times, ultimately leading to different costs.
Author: Linnemann, Thomas; and Vallana, Guido
Windenergie in Deutschland und Europa
[Wind energy in Germany and Europe: Status quo, potentials, and challenges in the baseload supply of electricity – Part 1: Developments in Germany since 2010]
In Germany, the installed nominal capacity of all wind turbines has increased eightfold over the past 16 years to 50,000 megawatts today. In the 18 most important European countries using wind energy today, the nominal capacity rose twelvefold to more than 150,000 megawatts.
One essential physical property of wind energy is its large spatiotemporal variation due to wind speed fluctuations. From a meteorologic point of view, the electrical power output of wind turbines is determined by weather conditions with typical correlation lengths of several hundred kilometres. As a result, the total wind fleet output of 18 European countries extending over several thousand kilometres in both north-south and east-west directions is highly volatile and exhibits a strong intermittent character. An intuitively expected significant smoothing of this wind fleet output to an degree that would allow a reduction of backup power plant capacity, however, does not occur. In contrast, a highly intermittent wind fleet power output showing significant peaks and minima is observed not only for a single country, but also for the whole of the 18 European countries. Wind energy therefore requires a practically 100% backup. As the (also combined) capacities of all known storage technologies are (and increasingly will be) insignificant in comparison to the required demand, backup must be provided by conventional power plants, whose economics are fundamentally impaired in the absence of capacity markets.
Windenergie in Deutschland und Europa: Status quo, Potenziale und Herausforderungen in der Grundversorgung mit Elektrizität – Teil 1: Entwicklungen in Deutschland seit dem Jahr 2010
Thomas Linnemann und Guido S. Vallana
VGB PowerTech, Essen, Deutschland
VGB PowerTech 6 | 2017
Download original document: “Windenergie in Deutschland und Europa”
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?”