Weighing Windpower

images/voice_uploads/orangeturbine.gif">Could wind energy be a viable source of electricity in North Carolina? Could it help improve our air quality? How much electricity could we produce and could we do it without negatively affecting the economy or the environment?

These are questions that the U.S. Department of Energy, N.C. State Energy Office, researchers at Appalachian State University and many environmental and energy organizations in the state and region are attempting to answer.

The wind has rapidly emerged as the world’s fastest growing power source, growing by more than 30% per year since 1996. The global capacity is now over 24,000 megawatts (MW), enough to power more than 10 million modern homes, with Germany, the U.S., Denmark, Spain & India being the major adopters.

Wind power is now the cleanest and cheapest way to produce electricity for many places in the world, but not without problems. Western North Carolina has close to a million acres of windy land adequate for electricity production, some of the most polluted air in the country.

In a recently conducted survey 75% of the residents indicated support for wind turbines. So why don’t we see any wind turbines and will we be seeing any soon?

American Windpower


There are now 27 states in the U.S. that have utility scale wind turbines. The installed wind capacity in the United States grew by 66% in 2001 with 1,696 new MW being added. We now have 4,265 MW of installed capacity in the United States, producing enough energy each year to power approximately 1 million households. The US wind energy represents about 20% of the world’s total, but despite the impressive numbers wind energy only produces about .3% of our nations electrical production.

However, our country could produce much more. The wind power potential in the U.S. is estimated to be at least 1 million MW. The goal of the American Wind Energy association and the Department of Energy’s Wind Powering America program is to see wind power produce 6% of our nation’s electricity by 2020, which would be 100,000 MW of capacity.

Many believe this is an obtainable goal. Denmark now produces about 18% of its electricity from wind power, Germany has twice the installed MW capacity of the US and some regions of Spain currently produce 50 % of their electrical needs.

The recent phenomenal growth of this energy resource can be attributed to several factors. Obviously the desire for greater energy independence from imported fossil fuels and a more sustainable, clean source of power are significant factors. Wind turbines are commercially available, they work reliably and quietly, they are modular and can be installed in just a few months, they have an estimated 25 –30 year lifespan, and they are compatible with agricultural and other land uses.

Another factor is the very competitive price of wind-produced electricity. The price of wind energy has declined from $.38 per kilowatt hour (KWH) in 1980 to $.03 to $.04/KWH in the best locations. Typical current prices are between $.04 and $.06/KWH. The U.S. DOE estimates that prices could decline another 30 – 50% in the near future. Once a wind turbine is constructed, the price of the electricity produced is stable and predictable, because the fuel source is free.

A variety of state and federal Policies have also contributed to the growth of wind power. Probably the most significant current program for utility scale wind technology is the Federal Production Tax Credit of 1.8 cents/KWH for wind-produced electricity. This program provides the credit for 10 years and is currently effective until the end of 2003. There are also some states with tax credits & rebate programs for wind energy. NC currently allows a 35% tax credit up to $10,500 for wind turbines.

Renewable Portfolio Standards (RPSs) have also been a factor in the growth of wind power. RPS require that a certain percentage of a state’s electricity come from green sources. Twelve states now have renewable portfolio standards and they have stimulated significant interest in wind energy. State Benefit Charges (SBCs) are another tool used to fuel the growth of wind energy.

These charges are essentially a small tax added to each KWH of electricity purchased. The money raised is used to support various “green” energy projects. Sixteen states currently have SBC programs.

Another program instituted now in 36 states is Net Metering, which allows small power producers, including residential turbines, to effectively receive the retail electricity rate for their power production. This dramatically improves the economics of renewable electricity.

A fourth factor stimulating the wind industry has been the growth of the green power market. These programs basically sell certified green power at a slightly higher price to individuals, families, companies & institutions wishing to support the development of green energy. There are a variety of approaches. The TVA has initiated their Green Power Switch program in 2000 and it has been successful. NC is now planning a statewide program.

Windpower In NC

North Carolina and the South in general do not show up on national reports describing states having significant wind resources. These studies tend to focus on windy land area. However, what we don’t have in quantity we have in quality. NC has some of the windiest land in the United States. And wind speed is the major determinant of the cost per KWH. Only 4.3% of the U.S. land area has class 6 or higher wind resources, which are areas where the average annual wind speed is higher than 14.3 mph 10 meters above the ground. NC has class 6 and even class 7 sites, as well as significant areas in the mountains & on the coast that are less windy but still windy enough for electrical production.

The newly made wind maps for North Carolina (www.wind.appstate.edu) shows all of the 24 western counties having wind resources adequate for electricity production. Good wind sites are typically at elevations over 3,000’ with an unobstructed, wide western exposure. The results of a recent analysis of the 24 western NC counties identified 138,000 acres or 2% of the land area having wind resources adequate for utility scale wind projects and 850,000 acres or 12.6% of the land area with wind resources adequate for residential scale systems.

The highest winds are found on the highest ridges or mountain peaks. Using only a small portion of this land would enable us in the western part of the state to produce most of our electricity and a significant portion of NC’s total consumption. Appalachian State University will soon be hosting a DOE-supported anemometer loan program, which will enable us to start collecting better wind data and more confidently identify viable sites.

While not as good, the coastal areas of NC also may be promising for wind power development. There are very good offshore wind resources in the Pamlico Sound and on the Outer Banks and beyond.

Gusty Challenges

The major problems that seem to arise during discussions of wind energy are noise, avian impacts, and visual pollution. Most agree that for the larger modern turbines being installed today, noise is no longer a concern in most cases. They make no noise when the winds are light and they are not rotating. At wind speeds between 4 – 7 m/s the noise from the wind in leaves, shrubs & trees will mask most of the sound from wind turbines.

Some have compared the noise of a wind turbine 350 meters from a residence to about the level of a kitchen refrigerator or a moderately quiet room, about 40 decibels. Turbine noise may carry further in downwind valley’s that are protected from the wind, however. I have visited four different wind farms on windy days this past year and could just barely hear the turbines when I was right next to them, and as I moved several hundred yards away I could not hear them at all.

The noise that one can barely make out when close to the turbines is not a mechanical noise, but a lower frequency natural swishing sound. There would be no problem conversing in normal speech at the base of the tower. They rotate very slowly at around 20 rotations per minute even in high winds and this slower rotational speed is a key aspect of noise control.

Turbine designers have also redesigned the tips of the blades to reduce noise. The tubular towers, upwind designs, streamlined, soundproof nacelles, & quieter gearboxes commonly used today also help to reduce noise levels. But because of the wide variation in the levels of individual noise tolerance there is no completely satisfactory way to measure the subjective effects of noise.

Small residential scale turbines have not made as much progress as their larger cousins in reducing noise, although improvements are being made and some are much quieter than others. Small turbines tend to have higher rotational speeds that vary with the wind speed and some make excessive noise while furling or governing during high winds.

Keeping Birds Safe


Avian or bird impacts have been another concern, especially after significant hawk mortality was experienced at wind farms constructed in the 1980s in California’s Altamont Pass. However, recent studies carried out at wind plants in New York, Vermont, Colorado, Oregon, Wyoming, Minnesota and California have found much less mortality. On average, 2 birds are killed per turbine per year for a total of about 33,000.

The TVA recently reported a higher mortality rate of 9.5 birds/turbine/year at their small 3 turbine wind farm on Buffalo Mountain, TN. They felt the numbers may be because there are higher numbers of migrating songbirds passing through that area than in most other windfarm locations.

While avian deaths are never desirable, these numbers are very low compared with the harmful impacts of other human activities on birds. Oil spills, global warming, mercury from coal fired plants, domestic cats, and collisions with vehicles, windows & tall structures are responsible for much more avian mortality than wind turbines. Estimates range in the hundreds of millions.

Today avian studies are routinely conducted before projects proceed and projects are planned to minimize avian impacts. Planning guidelines and other related information are being developed to make sure that avian impacts are minimized. A lot of information is available from the National Wind Coordinating Committee . Research is also being done to see if visual or auditory stimuli at the turbine location could help to prevent avian impacts and in some cases turbines are being turned off during critical times.

The visual impacts may turn out to be the most significant obstacle for wind energy in North Carolina. Most of the opponents of the recent TVA proposal to build a 13 turbine wind farm on Stone Mountain between Boone, NC and Mountain City, TN indicated that visual impacts and the potential indirect impact on the economy, especially real estate values were their primary concern. A recently completed survey of 400 residents of western NC also identified visual impacts as the major concern, although 75% of respondents still indicated support for wind power.

The impact on real estate values has recently been studied at 22 different locations around the country. The researchers were able to find no negative impact on real estate values and in some cases the land increased in value. The study documented several positive economic impacts related to one proposed project in Oregon; including annual tax revenues of $2.6 million, an 11% increase, over $12 million dollars in local spending on construction materials, food & lodging, and significant job creation.

Another recent study performed in Scotland examined the impact of wind turbines on tourism. They found 90% of tourists visiting Scottish beauty spots indicated that the presence of wind farms makes no difference to whether or not they would return and also found that twice as many people would return to the area because of the wind farm than would stay away.

The windiest spots in western NC and those likely to be able to produce economically acceptable electricity will be on ridges. Ridges over 3,000 feet are protected in NC by the Mountain Ridge Protection Act. This act prohibits the construction of any building, structure or unit more than 35’ above the crest of a protected ridge. There are exemptions in the act which include: “equipment for the transmission of electricity” and “structures of a relatively slender nature and minor vertical projections,” including windmills.

While windmills are mentioned as exempted, the NC Attorney General, Roy Cooper indicated in a letter to the TVA concerning their proposed project, that the 13 –16 wind towers “cannot be construed to fall within the exception…The legislature in 1983 had in mind, the traditional, solitary farm windmill which has long been in use in rural communities, not windfarm turbines of the size, type or certainly number proposed here…” Clarification of this interpretation and this Act will be necessary if we are to have any wind energy production in WNC.

Then Why Not Wind?


The wind is a sustainable and non-polluting energy resource that we are fortunate to have in NC. We have average wind speeds in our region that are among the best in the country. We could be producing clean, inexpensive, sustainable, home-grown energy with our wind resources now and forever.

The question of whether or not wind turbines can be legally constructed on mountain ridges needs to be addressed. They will not work well on towers shorter than 35 feet and the best spots will be on ridge tops. Do we really want to ban wind turbines in any location where they will work well? Wind projects can be carefully planned, controlled and monitored.

Modern wind turbines produce a very valuable resource, which we all use every day, without producing any air pollution. Each 1.5 MW utility scale turbine will effectively remove more than 7.5 million lbs of CO2 and 8.3 tons of NOX from our air every year. Sulfur dioxide emissions and water pollution will also be reduced.
They will also create significant wealth. More than $500,000 worth of green electricity will be created each year by every large turbine constructed.

Significant tax revenues, jobs and sustainable economic development can be created. To be able to produce electricity so inexpensively and at the same time so cleanly is a phenomenal technological achievement and one that deserves a closer examination than it seems to be getting.

Dennis Scanlin is a professor in the Department of Technology at Appalachian State University in Boone. For more information about wind power, check out www.nationalwind.org or see the American Wind Energy’s website at www.awea.org. Also, the DOE’s website at www.eren.doe.gov/windpowering.

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