Wind Power Impacts on Birds, Bats and Other Wildlife

1.    What are the impacts of noise from wind turbines on birds, bats and other wildlife?

Areodynamic noise of large wind turbine ranges between 500 Hz and 1000 Hz with a range of 30 to 60 dBA and an average of 50 dBA intensity (loudness). Most of the sound of wind turbines blades is white noise, similar to wind blowing through tree leaves at a level of normal traffic noise. Therefore wind turbines are likely to affect bird song, hearing and behavior as if they were exposed to urban residential traffic noise.

Research on birds’ ability to hear blades is still in its infancy, but preliminary results indicate that birds do not hear turbines as well as humans do (Dooling & Lohr 2000).

This is less of a factor than with earlier-generation wind turbines, as technology has lowered noise levels to a range comparable with the decibel level of an office environment

The very low frequencies, 4-16 Hz, (infrasound) transmitted through the ground could affect burrowing animals. Low frequency noises have been thought to be useful in bring earthworms to the surface and evicting moles. There been very little research on this phenomenon.

2. Does the construction and maintenance of wind farms have a negative effect on wildlife habitat?
Construction and maintenance impacts resulting from wind farms can be significant. Habitat fragmentation and conversion of pervious surfaces to impervious surfaces are two of the major impacts that can be expected from wind farm construction. Most access roads will need to at least 35 feet to handle the turning radius of the heavy equipment. A typical urban street is 26 feet wide and accommodates vehicular traffic in two directions. Accommodating these wide access roads in conjunction with additional infrastructure needs, like concrete platforms to set the turbines on, maintenance buildings, new power lines and substations all pose a significant impact on the landscape.

3. How is bird mortality estimated at wind farms?
Post construction bird mortality studies are difficult to evaluate. Each project and each state have developed their own protocol and what wildlife to focus on. California does not survey for small birds (only raptors) while Texas has not conducted any mortality studies to date. Adding to the uncertainty are two large variables, scavenging of dead birds and surveyor inefficiency. Both of these variables have been addressed through statistical models, but there remains a great need for an independent evaluation of post mortality studies and standardization of the methodology used.

4. Do monopole towers have different effects on birds than lattice towers?
Several advances in wind technology and application have reduced the risks posed to birds and other wildlife. Examples include the use of monopole towers rather than lattice-type or guyed structures, larger and slower-moving blades rather than small rapidly spinning ones, and widely spaced turbine arrays rather than dense ones.

Avoid Guy Wires and Lattice Supports. Guy wires should not be used for turbines, permanent met towers, or communication towers. Tubular supports with pointed or sloped tops should be used rather than lattice supports to minimize bird perching and nesting. Where met towers use lattice supports, they should be diagonal. Nearly all utility-scale wind turbines are monopoles, without guy wires. In one study, a researcher compared the likelihood of a bird with a one-foot wing span colliding with a guyed 343' communication tower as compared to a 300' extended height wind turbine with three 65 meter blades. The bird had three times the likelihood of collision with the guyed communication tower than the turbine with moving blades, assuming equal avoidance or attractiveness of both structures and with other important assumptions. This is likely one of the reasons avian mortality appears to be so much higher at many guyed communication towers. Communication and permanent met towers should be unguyed at turbine sites.

5. What is the range in numbers of birds killed per wind turbines annually at any given site? 
It is difficult to estimate the true impact to bird and bat mortality at wind farm projects. Most wind projects are required to conduct post construction mortality studies to assess the impact of wind farms and to undertake adaptive management strategies if impacts are viewed as too high. As more studies are conducted better information should become available.

Recent U.S. studies indicate that bird mortality at wind turbine projects varies from less than one bird/turbine/year to as high as 7.5 birds/per turbine/year. This means that between 10,000 and 40,000 birds may be killed each year at wind farms across the country – about 80% of which are songbirds, and 10% may be birds of prey. While not a large figure, local or regional impacts may be significant, and the rate of increase in turbine construction has conservationists concerned that new generators be built to standards that minimize the potential for bird kills. Bats are also subject to high mortality at wind farms frequently at considerably higher rates than birds.

According to a recent Seattle Times article (June 7, 2010) about 6,500 birds and 3,000 bats are killed annually by wind power projects in Washington and Oregon.

Between 1989 and 1991, 182 dead birds were found in study plots associated with wind turbines, and approximately 39 golden eagles per year were killed by turbines at Altamont Pass in California.  (Orloff & Flannery 1992).

At San Gorgonio pass, a California facility with 2,700 turbines located along the Pacific migratory flyway, Southern California Edison estimates mortality of 3900 to 6900 birds per year (McCrary et al. 1993).

Bat fatalities at wind energy facilities generally received little attention in North America until 2003, when an estimated 1,400–4,000 bats were killed at the Mountaineer Wind Energy Center in West Virginia.

Bat mortality ranges from 0.7 bats per turbine per year at the 38 turbines at Vansycle, OR to a high of 47.53 in 2003 at the Mountaineer Wind Energy Project in West Virginia. At the 16 turbines at Klondike, OR, bat mortality is 1.2; at Foote Creek Rim, WY, 1.3; at the 281 turbines at Buffalo Ridge, MN, 2.0; at the 31 turbines at Northeastern Wisconsin, 4.3; and at the three turbines at Buffalo Mountain, TN, 19.5. The high mortality rates at the 44 turbines at the West Virginia Mountaineer wind project and at the three turbines at Buffalo Mountain have created concerns throughout the country

6. How do bird mortality rates at wind farm projects compare to other sources of collision-related avian mortality?

The Cato Institute projects: "Ten thousand cumulative (emphasis added) bird deaths from 1,731 MW of installed U.S. capacity [as of 1995] are the equivalent of 4.4 million bird deaths across the entire capacity of the U.S. electricity market (approximately 770 GW)" (Bradley 1997), and uses this figure as argument against expansion of wind energy.

Furthermore, the American Bird Conservancy estimates that feral and domestic outdoor cats probably kill on the order of hundreds of millions of birds per year (Case 2000). One study estimated that in Wisconsin alone, annual bird kill by rural cats might range from 7.8 to 217 million birds per year (Colemen & Temple 1995).

The numbers of bird kills vary from project to project as well as the potential impact to bird populations. The critical questions that remain to be addressed include local impacts to bird populations especially raptors and avoiding high concentration areas, especially during migration. Better mortality studies are also needed to ensure accuracy of data.

7. How does the location of wind farms influence avian and bat mortality?
At the Altamont Pass WRA, turbines within 500 feet of canyons (prey areas) were found to be associated with higher raptor mortality. Mortality is also higher at turbines at higher elevations (Orloff & Flannery 1992). Many of the negative impacts on birds and bats can thus be avoided by assessing usage and avoiding those areas where wildlife use is predicted to be highest (Cade 1995). Site evaluation should include habitat quality, bird abundance, bird use, prey base, migratory movements, and night use (PNAWPPM-II 1996).

Also, as wind power projects become more prevent they will compete for space just like all other uses. Undertaking long-term planning efforts to minimize conflicts of use will be critical. Current the WA department of Natural Resources in the process of a wind energy mapping project that identifies those landscapes that may put wind power in conflict with other natural resources golas like the protection and recovery of threatened and endangered species like the Northern Spotted Owl and the Marbled Murrelet.

Many of the dead bat species use high-frequency echolocation calls to hunt insects. These high frequency calls attenuate quickly in the air, and it appears the bats may not have had time to move out of the path of a fast moving turbine blade by the time they detect it.

Even more bats may be killed by rapid air pressure reduction near moving blades that they cannot detect. Barotrauma involves tissue damage to air containing structures caused by rapid or excessive pressure change. One study found 90% of bat fatalities involve internal hemorrhaging consistent with barotraumas, while direct contract with turbine blades only accounted for half the fatalities

8. Do wind turbines running at night kill birds that migrate nocturnally?
Evaluations are needed of whether avian mortality at turbines follow the patterns of communication towers where over 90% of species killed are neotropical night migrants, with most mortalities during fall and spring migration at night. The effect of turbine characteristics should be evaluated further (e.g., do larger turbines result in increased per megawatt fatalities)

9. Are some species of birds more vulnerable than others to wind turbine mortality?
Golden eagles, red-tailed hawks and American kestrels had higher mortality than more common American ravens and turkey vultures (Orloff & Flannery 1992, 1996; Thelander & Rugge 2000, 2001). Deaths of eagles and potential danger to endangered California condors have raised the biggest issues at Altamont Pass.

Nine of the 46 U.S. bat species account for almost 90% of the bat deaths at wind projects and, while none of the nine are federally ESA listed, several of the species are in decline. It is not clear why some bat species seem susceptible to collisions with the turbines, and that information likely will be critical in developing effective preventative strategies.

Mitigation Opportunities

10. Is it possible to turn off the wind turbines or feather the blades during times of high bird migration? 
"Curtailment" is the term for changing operating periods to minimize impacts.  As a technical matter, this can be done, depending on the wind turbine (some turbines are not designed to be turned on and off).  Site-specific and species-specific studies about bird and bat migration and usage patterns would be needed as the basis for curtailment strategies, since conditions are so site-specific.  In addition, there are other operational and economic issues.  For example, given the current economics of wind power, there might be economic issues with reducing generation time.

One current type of curtailment receiving attention - specifically to address bat mortality - is changing the cut-in speed (the wind speed at which the turbine blades start rotating).  Because bats and their insect prey are more active when wind is lower, the thought is this approach might make a significant reduction in bat mortality.  The Bat and Wind Energy Cooperative  (http://www.batsandwind.org/) is involved in this research.   One operational advantage of this strategy is that it can be included in the operating plan from the beginning and so represents a cost that operators can budget for with some certainty.  (By contrast, curtailment for bird migration -  because these would be so site-specific and contingent - would not be as easy to plan for up-front.)
Wind Power Permitting in Washington State

11.       What is the basic permitting process in Washington?
In Washington, permitting wind farms is made even more complicated by the fact that project developers can choose to use either state or local permitting procedures. Usually, the developer applies for local land use approval from the county where the wind farm will be built. But the developer may also seek approval from the state’s Energy Facility Site Evaluation Council ("EFSEC"). This state agency was intended to provide a more streamlined permitting process, though it has not always worked as planned.

The permitting of wind project also must follow the State Environmental Policy Act (SEPA) and National Environmental Policy Act (NEPA) process as required. These are often completed concurrently with either the county or state process. 

12.  What is the County Conditional Permitting process entail?
Most counties with wind resources have amended their local land use codes to allow wind farms as a "conditional use" in their agricultural and forest lands. These counties then adopt a process for reviewing and approving "conditional use permits" for individual projects that are proposed for the agricultural and forest lands. In other words, a wind farm is not automatically allowed in these lands. It is allowed only if the county decides that it meets whatever conditions the county thinks are appropriate. It is subject to the environmental review requirements of the State Environmental Policy Act (SEPA), which means that an Environmental Impact Statement (EIS) could be required if there are significant environmental impacts. It does not provide the one-stop permitting available under the Energy Facility Site Evaluation Council (EFSEC) process, so the project applicant must apply separately for any other permits that are needed.

13. What does the State Energy Facility Site Evaluation Council (EFSEC) process entail?
EFSEC was established for one-stop shopping for wind power project approvals.  The process is responsible for SEPA, and if a federal approval is required NEPA, compliance. The process is very formal and includes an adjudicative hearing with the availability of concerned parties to intervene and become part of the official process. The goal is to create a site certification document that spells out all the steps the project proponents must cover as they construct the project. The Governor has the final say and the most controversial part of the EFSEC process is that the state agency can recommend that the Governor preempt local land use requirements. Preempting local rules is politically difficult, but it provides an alternative to the local process in some cases.
 
The site certification document is a binding agreement between the applicant and the state that conditions approval of an energy facility location on the applicant’s assured compliance with certain regulations related to the construction and operation of the facility
Appeals of Site Certifications
A party may file a petition for review of the Governor's final decision in Thurston County Superior Court. RCW 80.50.140(1)

14. Can I install a personal wind turbine on my property?
It depends on where you live.  According to the U.S. Department of Energy’s  “Consumer’s Guide to Small Wind Electric Systems,” and the “WDFW Wind Power Guidelines”some of the things to consider are:

Is there enough wind where you live?  At least Class II winds (9.8 –11.5 mph) are needed for efficient energy production. The strongest winds usually occur along the seacoasts and on ridge tops.
Do you have enough space for a wind system?  Generally, small wind systems require at least an acre to allow an appropriate distance from physical barriers and setbacks from the property line, utility lines and /or road right-of-ways. 

Does the zoning code allow you to have a tall enough tower ?  The tower height needs to be at least 30 feet above any physical wind barriers such as trees, buildings, or bluffs that are within 300-500 feet to avoid air turbulence. In addition, winds are stronger at greater heights so tower heights of 65-140 feet are common.

Impacts to native habitats and species, as well as migratory species also need to be considered, especially near or within environmentally sensitive areas.  Consultation with WDFW is encouraged to avoid and mitigate these impacts.

15.     How do I obtain a copy of the revised WDFW Wind Power Guidelines?

The guidelines are available at  http://wdfw.wa.gov/hab/engineer/windpower/index.htm
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Wind Power Alternative Technologies
16. What kinds of new turbine designs are being explored to minimize/stop the toll on birds and bats?
There does not seem to be much (if any) research into different turbine designs for larger utility-scale turbines (larger than 1 mW) to minimize the toll on birds and bats.  The horizonal access turbines currently in use are considered by industry to be significantly more efficient than, for example, vertical access turbines.

There are several companies developing vertical access turbines for the small wind turbine market (less than 100kw), or mid-size wind turbine market (100kW to 1 mW), and some of these promote them as less harmful to birds (http://peswiki.com/index.php/Directory:Vertical_Axis_Wind_Turbines).

On May 25, 2010, the Department of Energy announced a $6 million program to advance midsize wind turbine technology in order to boost the speed and scale of midsize turbine deployment.  The specifications do not appear to include any focus on wildlife impacts, but instead focus on commercial potential, creating US jobs, etc.

 
17. What other kinds of wind technologies (other than turbines) are being explored to reduce bird and bat impacts?
The major focus in reducing bird and bat impacts is in siting.   For example, the American Wind and Wildlife Institute mission is focused on "best practices in wind farm siting and wildlife habitat protection" (http://www.awwi.org).

Relative to technology, in addition to the research on increasing cut-in speeds, two other areas of research focus include:

1)  Emitting acoustic deterrent signals, to disrupt bat movements towards the turbines.  NREL is currently in the 1st year of testing this technology, with some promising initial results.  It is not yet clear if this could be applied in some similar way for birds.

2)  UV-light reflective paint on wind turbines.  NREL supported in-lab research that seemed promising, and then some initial field study in this area, which did not have any clear results.  Currently this area is not being actively funded, but it might be promising.

18. Why are bird and bat studies necessary for projects that use the new generation turbines, which are much taller and have slower rotor speeds? Don't these new turbines have much lower impacts to birds?
During California's early wind energy development turbines were relatively small, spaced closely together, with the rotors spinning at high speeds. Wind turbines installed at the Altamont Pass Wind Resource Area, San Gorgonio, and Tehachapi during the 1980s generally had an installed capacity of around 100 kilowatts, reached heights of approximately 50 feet from the ground to the tip of the extended rotor, with blades spinning around 30 revolutions per minute (rpm). The new generation turbines (installed capacity around 1.5 megawatts) can be as tall as 450 feet from ground to rotor tip, with lower rotational speeds ranging from 15-27 rpm and tip speeds of approximately 200 feet/second. 

A number of researchers hypothesized that these new-generation, taller turbines would reduce wildlife impacts, in part because birds would be better able to see and avoid the slower-spinning blades. As studies have been conducted on "repowered" sites, where old turbines were replaced with the new, large turbines, it appears that impacts to some species such as golden eagle are reduced. However, impacts to raptors such as red-tailed hawks and American kestrels do not seem to have declined. Other researchers have analyzed bat fatality data as a function of turbine height and found that as turbine height increases, more bats are killed possibly because the taller turbines reach into the airspace used by migratory bats.
Many factors affect the collision risk to birds and bats at a wind resource area, including turbine variables (size, rotational speed, operational time, rotor swept area, spacing, tower type), habitat, and bird/bat use. Research is currently underway to clarify which of those factors might be consistent predictors of bird and bat fatalities, but it will probably never be possible to assume that a particular turbine type is so risk free that no studies are needed to assess that risk.

Wind Power Basics

19.  What is wind power?
Wind power is the conversion of wind energy into a useful form of energy, such as using wind turbines to make electricity, wind mills for mechanical power, wind pumps for pumping water or drainage, or sails to propel ships.

20.  What is a megawatt?
Watts (W) are the units for measuring power. A megawatt (MW) is one million watts and a kilowatt (kW) is one thousand watts. Both terms are commonly used in the power business when describing generation or load consumption. 

A one hundred watt light bulb is rated to consume one hundred watts of power when turned on. If such a light bulb were on for four hours it would consume a total of 400 watt-hours (Wh) of energy.  Watts, therefore, measure instantaneous power while watt-hours measure the total amount of energy consumed over a period of time.  The average U.S. household consumes a little more than10,000 kWh of electricity each year.

21.  How much electricity can one wind turbine generate?
The output of a wind turbine depends on the turbine size and the wind speed through the rotor. Wind turbines being manufactured now have power ratings ranging from 250 watts to 5 million watts (5 MW).

A 10-kW wind turbine can generate about 10,000 kWh annually at a site with wind speeds averaging 12 miles per hour, or about enough to power a typical household. A 5-MW turbine can produce more than 15 million kWh in a year--enough to power more than 1, 400 households.

22.  How many turbines does it take to make one megawatt?
It depends on the power rating of the turbines.  It would take ten 100-kW turbines to make a 1-MW wind plant.  Most utility-scale turbines are in the 700-kW to 2.5-MW range. Ten 700 kW turbines would make a 7 MW wind plant while ten 2.5-MW machines would make a 25-MW facility. 

23.  How many homes can one megawatt of wind energy supply?
An average U.S. household uses about 10,655 kilowatt-hours (kWh) of electricity each year. One megawatt of wind energy can generate from 2.4 to more than 3 million kWh annually. Therefore, a megawatt of wind generates about as much electricity as 225 to 300 households use. It is important to note that since the wind does not blow all of the time, it cannot be the only power source for that many households without some form of storage system. The "number of homes served" is just a convenient way to translate a quantity of electricity into a familiar term that people can understand.

24.  How much does wind energy cost?
Over the last 20 years, the cost of electricity from utility-scale wind systems has dropped by more than 80%.  Currently, state-of-the-art wind power plants can generate electricity for less than 5 cents/kWh with the Production Tax Credit in many parts of the U.S., a price that is competitive with new coal- or gas-fired power plants.  By comparison, existing hydroelectric projects in the Pacific Northwest can generate power for less than 1 cent/kWh, although the cost of constructing these projects is greater.