Frequently Asked Questions About the Brewster Project (For the Basics of Wind Energy FAQs page, click here)
To see the Powerpoint presented on September 13th as part of the SelectBoard informational presentation, click here.
To see the video recording of the September 13th SelectBoard informational presentation, click here.
To view the answers to citizen submitted questions concerning the CVEC Wind Turbine application at the 1/31/11 Selectmen’s Meeting, click here.
FAQ: Freeman’s Way Turbine Installation
1. What will be the distance to the closest residence?
Answer: The closest residence will be over 1,800 feet away from Turbine A. Click here to see a distances map illustrating neighborhood distances from the Freeman’s Way industrial area. Click here to see a chart demonstrating the distances of residents from neighborhood turbines in the towns of Portsmouth, Hull, and Bourne. No complaints have been made to officials in Portsmouth, Hull, or Bourne.
2. Why won’t Brewster experience the issues reported by some Falmouth residents?
Answer: The sound profiles for the two projects are quite different due to the Brewster project’s sheer distances from residents, the less high terrain, proximity to Route 6, and turbine technology. The Brewster project’s sound studies demonstrate sound profiles well under regulated limits at property bounds and at nearest residences.
In addition to the physical differences in the sites, the machines proposed for the CVEC Brewster wind project will be the V90 1.8 MW, a pitch-regulated wind turbine, while the Falmouth wind turbines are the Vestas V82 1.65 MW, a stall-regulated (active stall with hydraulic pitch cylinder technology) machine. The difference in pitch-regulated versus stall-regulated turbines is summarized in a 2010 document entitled “Guidance Note on Noise Assessment of Wind Turbine Operations at EPA Licensed Sites (NG3)”:
“In general, noise from wind turbines increases with wind speed and rotational speed. Most modern wind turbines are pitch-regulated variable speed turbines, which have a characteristic noise profile of steeply increasing noise with wind speed up to the point at which the turbine is generating its ‘rated power’ or maximum power, above which there is usually no increase in noise. For ‘stall regulated’ machines, noise can increase considerably above rated power of the turbine and such designs are becoming less popular as a result.”
The V82 1.65, while considered a highly reliable and very productive wind turbine with over 2,000 in use in the United States, underwent at least five generations of advancements before Vestas planned to stop manufacturing in favor of more advanced technology platforms.
Each IEC certified wind turbine has its own unique sound power curve, which is published by the manufacturer. It is fair to characterize the V-90 1.8 MW wind turbine as a quieter wind turbine over the Vestas V82 utilized in Falmouth.
To see a detailed comparative analysis between Falmouth and Brewster, click here.
3. What is the “sound” level that will come from the proposed turbines at Brewster’s Industrial Park?
Answer: Sound modeling for the proposed turbines has been finalized. The turbine siting is well in accordance with all state and local requirements regarding sound levels at the property bounds. With the great distance from the industrial installation to residential areas afforded by the Freeman’s Way industrial park siting, sound is not anticipated to be a problem. To view a map with the sound sampling sites illustrated and the results for closest residences, click here.
4. What is infrasound and is there any reason for concern about infrasound?
Answer: Sound levels are expressed in units called decibels (dB). The decibel is a logarithmic quantity that relates the sound pressure from a source to a reference sound pressure. An important characteristic of sound is its frequency, or “pitch,” which is expressed in units known as hertz (Hz). In terms of frequency or pitch, sound can be categorized as audible and inaudible. The human ear is most sensitive to sounds that occur over a range of frequencies from 20 to 16,000 Hz. Infrasound is commonly defined as frequencies below 16 Hz, and is generally inaudible to the human ear.
Currently there is no evidence of health effects arising from low frequency sound known as infrasound.1 Infrasound is all around us. Car engines, waves hitting the shore, and home appliances like refrigerators and washing machines all emit infrasound.
Assumptions used in the sound analysis made for the Freeman’s Way Industrial Park Wind project yield projections of wind turbine sound levels that are conservatively “high”. For example, the projected levels due to operation of the wind turbines exclude the effects of excess attenuation due to propagation over acoustically “soft” ground and the excess attenuation due to ground vegetation. Also, the sound propagation algorithms within the noise prediction model assume an omni-directional downwind condition. That is, although it is physically impossible, the noise prediction model assumes that every point for which a sound level is computed is downwind of the turbines.
Low frequency sound was considered when performing the Freeman’s Way Industrial Park Wind Project sound modeling, with sampling in octaves as low as 16Hz. The noise assessment utilized sound power levels for the wind turbine, which were provided by the manufacturer, and used as input to the model. The model predicted operational sound pressure levels from the turbine at selected locations in the community and along the property line of the facility, The study demonstrates that low frequency sound pressure levels will be similar to existing ambient sound levels in the community.
Concerns relative to the CVEC Brewster wind proposal and sound whether at low or high frequencies, are minimized due to the Brewster project’s location, with most homes minimally over 2,300 feet distant from the turbines. The sound analysis which was performed demonstrated any increase in unweighted sound levels due to the Project will be well below the Mass DEP noise limits. .
Notwithstanding, complaints, should any arise, can be raised with the Town as the landowner. Then the Town and CVEC would make every effort to deal with the complaints accordingly.
DTI, 2006; CanWEA, 2009; Chatham-Kent Public Health Unit, 2008; WHO, 2004; EPHC, 2009; HGC Engineering, 2007.
5. What is shadow (or flicker) and what will be the effect on the closest residences?
Answer: “Shadow flicker” can occur when the blades of a large wind turbine pass between the sun and the observer, causing an on-again, off-again shadow to be cast by the blades. The flicker can be annoying when trying to read or watch television. If any effect is experienced, it is generally short-lived due to the moving path of the sun, incidence of cloud cover, and wind-driven angling of the turbine sideways to the sun.
While shadow should not be a concern due to the remote location of the Freeman’s Way industrial site, an engineered shadow study for the Freeman’s Way project has been produced. Any shadow that will fall has been assessed and the number of minutes per year the shadow will be present is known. Click here to see a map with a chart.
6. How tall will the turbines be and how will these turbines compare in height to the existing cell towers in the Freeman’s Way industrial area?
Answer: The tower heights will each be 265′ to the hub, or nacelle, which houses the generator and computer. The rotating blades of the turbines will add 145‘ to the tower height making the total height about 410’ with a blade fully extended. Simulations (click here to see simulations) have been produced to demonstrate the impact of the two turbines on the views of the industrial park from the surrounding area.The existing communication towers in Brewster’s Freeman’s Way stand 262’ and 309’ tall. Click here to see the site map illustrating the installation site in the industrial park next to the communication towers.
The existing communication towers are a good indicator of views from which the turbines will be visible. When viewing from vantages around town, where the existing towers are visible, it can be assumed that the turbines will be visible. However the 410-foot tall turbines in the Freeman’s Way Industrial Park will not be the tallest structure in the area. The communication tower at exit 12 in Orleans will remain the tallest structure in the area at 495 feet.
7. What kind of illumination will be on the proposed turbines and/or towers?
Answer: The Federal Aviation Administration will likely require a medium intensity red blinking beacon, similar to those on water towers and to those on the cell towers in Freeman’s Way. The light will be on the hubs of the turbines at about 265′.
8. What are the safety issues with turbine blades and their potential failure and ejection from the turbine toward offsite objects? Can there be ice thrown from the blades?
Answer: While blade failures have occurred in rare circumstances, these have been on vintage units with older blade composite technology and faster rotating blades. The normal operational speed of the proposed turbines is about 9 to 15 revolutions per minute (rpm). The setback of 410′ from the public and structures is appropriate based on industry practice and insurance company standards.
The potential for ice to accumulate and be thrown off blades as they spin, does exist. However, the turbine is built to sense any ice buildup, which slows the turbine’s rotation, causing the turbine to automatically shut down. Ice throw is also rare and the setback accommodation in the Freeman’s Way Wind project should provide for any unusual incidence.
9. Are there plans for additional turbines down the road?
Answer: CVEC is not aware of any plan for CVEC, Brewster or any other entity to bring forward further municipal wind projects on Brewster land.
10. What will be the electromagnetic field around the turbine and what will be the EMF effect on the local environment?
Answer: An electromagnetic field (EMF) is produced by any wire carrying electricity. Electric fields from the wind turbines will be quite low since the voltage at which the power is generated will be low (around 600V.) The interconnection to the “grid” (the power line grid running across the Cape) will be made at 23,000 volts, which is the same voltage as the wires that run in front of most homes at 40 feet above the ground.
11. What will be the voltage of the overhead interconnect?
A typical large wind turbine generates alternating current (AC) power at 579 – 690 volts (3-phase.) The voltage is stepped-up through a transformer to 23,000 volts, which is the existing distribution voltage on most of Cape Cod.