Up in the air- Challenges in siting wind projects
Wind is merely air in motion. A marvel really, because that "air in motion" can be converted to electricity - renewable power for our homes, farms and businesses.
Basin Electric Power Cooperative
- March 23, 2010
By Andrea Blowers, Basin Electric staff writer/editor
Wind is merely air in motion. A marvel really, because that "air in motion" can be converted to electricity - renewable power for our homes, farms and businesses.
Seems simple enough - go where the wind is, build a turbine and let the electricity flow, right? Not so. Like any other form of power generation, building a wind project, from concept to commission, has its challenges.
Ron Rebenitsch, Basin Electric manager of alternative technologies, says to even consider building a wind project, three main filters must be addressed: siting, transmission and environmental concerns. "First, siting is critical. Do you have the wind?" he says. "You need to pick sites carefully. A one mile per hour in average annual wind speed can change production by 15 percent. That's a potential $50-million impact over the life of a 100-megawatt project," Rebenitsch says.
"Second is transmission. For a project to be viable, it needs a firm transport, and the cost to upgrade a transmission system is very expensive," he says. A 100-megawatt project is too large to interconnect to most rural distribution lines and needs a high-voltage transmission line, typically 115 to 230 kilovolts. The cost of building it suggests the wind project needs to be sited between 10 and 15 miles from that line.
"Finally, you need to be aware of the environmentally sensitive areas and make every effort to avoid them," he says.
These three elements are major challenges in and of themselves, but some of the more dubious issues with constructing a wind project relate to the elemental details. Those include landowner concerns; public opposition because of turbine noise, shadow flicker or viewshed; environmental and cultural preservation; and avian mortality.
The elements of opposition
"Who actually owns the wind? That's an issue that hasn't yet been clearly defined," Rebenitsch says. And it's emerging as a major policy issue for state legislators and regulators. "The allocation of property rights related to wind could rival the historical 'water wars' of the West," he says.
Wind is a free-flowing natural resource that crosses property boundaries and is not "owned" by anyone, nor is it "produced" on any one property. "Currently, wind project payments to landowners for wind leases are primarily for use of the surface estate, not for the wind," Rebenitsch says.
One of the important issues is spacing between the wind turbines because of such things as the downwind or wake effect.
Rebenitsch explains a common size wind turbine of 1.5 megawatts can have a 70- to 82.5-meter rotor diameter (230 to 270 feet). "We try to maintain a minimum of five rotor-diameter spacing in the predominant wind direction and avoid siting other turbines within 385 meters (1260 feet)," he says. "Crosswind spacing in the non-predominant wind direction can be closer, but even then, we strive for a minimum spacing of three rotor diameters."
Unfortunately, the need for spacing between wind turbines does not address property boundaries. "As a result, rights to the flowing airstream and allocation of those rights, financial and otherwise to different property owners, can become an issue," Rebenitsch says.
Rebenitsch says regulatory certainty needs to be established. He proposes using one of two models: "first in time; first in right" or unitization. "Just as wildlife is considered a public resource and is regulated by the state, wind is also a public resource. Its use will need to be allocated with regulatory certainty," Rebenitsch says.
Other issues challenging wind project development voiced by landowners and the general public include turbine noise, shadow flicker and viewshed.
"Nearly everything that has moving parts will make some noise; wind turbines are no exception," Rebenitsch says. The sounds emitted from wind turbines can be mechanical or aerodynamic. Today's turbine designs effectively reduce mechanical sound through sound proofing; therefore, the aerodynamic or "whooshing" sound is what one normally hears.
Rebenitsch says permits and industry practice limit the level of noise that can be created by a wind project. "It's different for each project, but generally it's less than 50 decibels at the nearest residence. That's comparable to the inside of a typical home." The American Wind Energy Association states the typical wind turbine falls in the range of 35 to 45 decibels at a distance of 350 meters. For a point of reference, a very quiet library measures at 30 decibels and a typical neighborhood at 45 decibels.
Wind turbines can also cause shadow flicker. Shadow flicker is the effect resulting from the shadows cast by the rotating blades of the turbine on sunny days. "It can be irritating, and our siting of turbines minimizes it. But even then, it can happen for a few minutes in the morning and evening during certain times of the year," Rebenitsch says. It's more or less pronounced depending on the intensity of the sun/shadow contrast and the distance from the turbines to a receptor. The effect is typically more pronounced if one is closer than 1,000 feet from a turbine, but most turbines are located at least 1,400 feet from any residence.
Through computer modeling, Rebenitsch says every effort is made when siting each turbine to minimize or eliminate shadow flicker as much as possible. More opposition comes when one considers the visual impact on the landscape. Landowners who think the sleek glistening turbine blades on the horizon are an eyesore can raise objections that may make it difficult for a project to move forward, depending on local public sentiment. Viewshed is of great concern for property owners, specifically those who want a pristine view of the land.
However, in 2009 a Texas court ruled on the issue of viewshed, where nearby landowners filed suit claiming impacts to their views. The court essentially ruled that property rights to viewshed "end at the property line."
Environmental battles
Challenges for wind project developers aren't spurred only by landowners and the public; government agencies and environmental groups also offer their fair share.
Though each turbine of a wind project requires very little actual land space, an entire wind project can spread over many miles. According to Lyle Witham, Basin Electric manager of environmental services, to ensure all environmental and cultural impacts are addressed, one or multiple federal agencies is charged with determining the viability and/or mitigation requirements for a project. First, the agency decides what needs to be completed - an environmental assessment or an environmental impact statement - depending on the scope and possible impact of the project.
In general, a smaller project requires an environmental assessment. The financial burden for this permitting process is between $500,000 and $800,000, and approval can take anywhere from 18 months to two and a half years. For a larger project, however, expect an environmental impact statement and permitting costs of $1 million-plus, and two to four years for approval.
In addition to the environmental studies, project developers need to complete a Section 106 consultation of the National Historic Preservation Act - avoiding historical, archeological and cultural properties. "In the Upper Great Plains, there were numerous nomadic tribes; each tribe might have cultural resources located on various areas of the land," Witham says.
He explains a number of federal agencies may get involved in the environmental studies of a project, including the U.S. Fish and Wildlife Service for endangered species, the Department of the Interior if the project crosses national park land, the Bureau of Land Management and others. Typically, the Fish and Wildlife Service becomes involved in the review of potential wind energy developments on public lands - as a cooperating agency or because of its responsibilities under the Endangered Species Act.
Witham says, in general, there are two big sets of environmental issues for wind projects. The first is the impacts on wetlands and native grasslands. The second is the
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(Click to enlarge) This map shows the annual average wind power estimates at 50 meters above the surface of the United States. It is a combination of high resolution and low resolution datasets produced by NREL and other organizations. The data was screened to eliminate areas unlikely to be developed onshore due to land use or environmental issues. In many states, the wind resource on this map is visually enhanced to better show the distribution on ridge crests and other features. The purple shaded area in the center of the wind resource map depicts the flyway for whooping cranes and other migratory birds. |
The flyway creates a significant challenge because claims have been made that wind turbines cause avian mortality. Rebenitsch says this has haunted the wind industry since the 1980s when early wind turbines used lattice structures, which provided attractive roosting for birds. Birds, particularly raptors, often used the latticework to roost while watching for prey. When they would dive for their prey, they would be struck by the turbine blades. Also, at that time, the turbines were made with high speed rotors and the blades spun much faster, making them less visible.
Since then, the turbine structure has changed; they are tubular with smooth surfaces and blade rotation speed has slowed down considerably. And as Rebenitsch explains, there has never been a recorded case of whooping crane or sandhill crane death from a wind turbine. "In fact, avian mortality rates due to wind turbines is very low, especially compared to other sources of avian mortality, such as buildings, cars and feral cats."
Like any other energy resource, developing wind energy is not without its challenges. And like any other energy resource, there are societal benefits and tradeoffs. "There's not a black and white to this, there are various shades of grey," Rebenitsch says. "We're in an energy-intensive society, and our lifestyle relies upon inexpensive energy. Wind is just one resource. It's not THE answer; it is one of many answers."
Downwind or wake effect
Large wind turbines produce a downwind or wake effect on the airflow as it passes the turbine blades. This effect reduces the amount of energy that could be extracted by nearby turbines.
When this downwind effect crosses property boundaries, the determination of who has priority rights to the energy in that airflow becomes an issue.
In addition, the downwind effect of additional turbulence in the airstream can produce additional stresses on nearby wind turbines. Where turbines have insufficient spacing, turbine manufacturers dictate operating limits to mitigate the stresses caused by the turbulence. In turn, that reduces production.
"First in time; first in right" vs. unitization
One possible model, "first in time; first in right" allocates the resource based on the order in which users demonstrate beneficial use of the resource. It's similar to the model used to allocate scarce water resources in the West. If a wind turbine is built, it would have first rights to the energy in the flowing air within a reasonable distance around the turbine.
Another model might be "unitization," which has been used in the oil industry. In this model, an area of influence caused by the development of an oil field is determined and that area is unitized. In a unitized oil field, the resource owners in that region submit their resources to a common development and receive the benefits and output in a share proportional to the portion of the resource they submitted.
In any case, avoiding "not in my backyard" veto power is important to the development of the wind industry.
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