Wind power

BACKGROUND

Overview: Wind power is a renewable energy source that is generated from wind. It does not deplete natural resources, such as coal, gas, water, or oil. Additionally, wind farms are usually retired and dismantled after 20-30 years of operation; once retired, they generally do not leave pollution behind at the site.

The production of wind-powered electricity does not create air or water emissions, or hazardous wastes. In contrast, traditional electrical generator plants produce sulfur dioxide; sulfur dioxide emissions have been linked to acid rain, which has negative environmental effects on forests, lakes, and wildlife. Acid rain is also linked with the corrosion of buildings and bridge structures. Nitrogen oxide, released by the burning of natural gas, contributes to smog. Carbon dioxide is another "greenhouse gas" that has been connected to global warming, changing weather patterns, droughts, and floods.

The American Wind Energy Association estimates that if the United States were to generate 24 billion kilowatt-hours of electricity by wind, it would prevent 30 billion pounds of carbon dioxide, 76,000 tons of sulfur dioxide, and 36,000 tons of nitrogen oxide from being released into the atmosphere.

Coal, one of the most polluting fossil fuels, is currently used to generate more than half of all electricity in the United States (52%); natural gas produces 16% of all U.S. electricity, nuclear power produces about 20%, and hydropower produces only seven percent.

According to the American Wind Energy Association, developing 10% of the wind potential in the 10 windiest states may provide more than enough energy to displace the emissions from coal-fired power plants.

At this point of development, many wind turbines are used to supplement existing energy plants, which use consistent electricity sources such as coal, gas, or nuclear resources. However, research suggests that connecting 10 or more wind farms could produce an average of 33% of the U.S.'s electricity, as long as a minimum level of wind speed and turbine height is in place.

At the Earth's surface, different locations have different wind speed distributions. The consistency of wind speed varies not only from site to site, but from season to season and hour to hour. This variability poses the biggest challenge to effectively harnessing wind energy for mass electricity production and is the focus of many current global research efforts.

History: Wind power has been used throughout history to propel sailboats, pump water, and grind grain. The Babylonian emperor Hammurabi used wind power to irrigate crops. Windmills date back as far as the 7th Century in Afghanistan. As early as 1219 AD, China used windmills for grinding grain.

The traditional Dutch windmill came into use extensively in northwestern Europe in the 1380s. These mills required a live-in keeper who had to turn the sails to maintain the correct position for the wind. During storms, the wind keeper would have to furl the sails, much like a sailboat.

By the era of pre-industrialism in Europe, wind power had many uses: to pump water for consumer use; for irrigation; for the grinding of grain; for the milling of lumber; and to assist in the processing of spices, cocoa, paints, dyes, and tobacco.

In the United States, the windmill was used to draw water for farms and to supply water for railroad engines. The familiar windmill of the western American farmland was built by the Halladay Company in 1854 and is still in use today.

In 1888 in Cleveland, Ohio, Charles Brush constructed the first large windmill to generate electricity. This windmill successfully operated for 20 years.

Windmills became less prominent in American farm life in the 1930s, after the Rural Electrification Administration's program brought electrical power to small farmers who were struggling through the Great Depression.

However, even as late as the 1940s, windmills were finding a place in electrical production. A mountaintop in Vermont, called Grandpa's Knob, was home to the largest turbine of that time; it created electrical power for the local utility during World War II.

Since World War II, wind turbines and their popularity have fluctuated. As abundance and shortages of fossil fuels have led to unstable energy costs, the demand for cheaper alternatives has increased.

The first modern windmills were built in the early 1970s by the Danish manufacturers Kuriant, Vestas, Nordtank, and Bonus. U.S. efforts began again after the 1973 oil embargo. The Federal Wind Energy Program and NASA began researching wind energy as an alternative power source.

By 1981, misunderstanding of the technical elements of wind power and impatience with the progress of wind production levels led to decreased federal support by the Ronald Regan Administration.

In 1989, under the George Bush Administration, the National Renewable Energy Laboratory (NREL) focused on improving the earlier designs of the 1980s.

In California, more than 17,000 wind turbines were installed between 1981 and 1990.

In 1999, President Bill Clinton issued an Executive Order that instructed federal government agencies to support renewable energy when making energy purchases. The U.S. Army also announced that it intended to develop wind energy at Fort Bliss, New Mexico.

In 2003, Federal Reserve Board Chairman Alan Greenspan testified before congress that rising natural gas prices were threatening the economy's future. Experts supported the opinion that alternative energy options would make economic sense. Meanwhile, research and installation of windmills spread throughout Europe, with Germany, Sweden, and Denmark leading the pack.

Design improvements are continuing today, with wind power being the fastest growing segment of energy production worldwide.

Wind power is now considered the least expensive and most practical alternative to traditional power sources. As the most developed renewable energy technology, it also has the shortest construction time of any power plant option.

Wind power in the United States: The U.S. Department of Energy (DOE) reports that utility-scale wind energy production in the United States has gown at a rate of 30-40%, increasing from 2,500 megawatts (MW) in 1996. By 2008, the United States installed 25,170MW of wind power capacity. Texas had 7,116MW installed, while Iowa and Minnesota had over 1 gigawatt (GW).

California previously held the record for the most American wind power development, but in recent years, Texas has surpassed that achievement. Other states that have active wind plants are Iowa, Kansas, Massachusetts, Minnesota, Nebraska, New Mexico, New York, North Dakota, Oklahoma, Pennsylvania, South Dakota, West Virginia, Wisconsin, and Wyoming.

DOE studies project that wind energy produced in the plains of Texas, Kansas, and North Dakota may provide sufficient total energy for the entire United States. Even using today's technology, the DOE states that wind resources around the Great Lakes could potentially provide as much as 80% of needed power: This is the amount that the United States currently produces with traditional resources such as gas or coal.

Furthermore, according to the DOE, the world's winds could supply almost 15 times the world's current energy needs. It is estimated that 72 terawatts (one trillion watts) of potential wind power exists on the planet.

Wind power internationally: The top 10 countries employing wind to generate electricity are the United States, Germany, Spain, China, India, Italy, France, the United Kingdom, Denmark, and Portugal. Denmark generates almost one-fifth of its total electricity with wind turbines, leading the world in the percentage of energy produced through wind. The Netherlands, Japan, and China are also actively pursuing wind energy.

The Global Wind Energy Council (GWEC) estimates that the global annual market for wind energy has grown at a rate of 31% since the early 1970s; it has grown by 32% in 2006 alone.

By 2010, the World Wind Energy Association expects a 21% growth in wind power production, reaching160GW of capacity installed worldwide. However, increasing global concern over the cost of fossil fuels has some experts projecting percentages that may far exceed these figures.

In 2007, the Princess Amalia Wind Farm in Holland was the first to produce off-shore electricity for that nation, located 23km (14.29 miles) off the Dutch coast.

As of 2008, Europe leads the world in the number of off-shore wind farms. Enjoying strong winds and shallow coastal waters in the North and Baltic Seas, Denmark in particular has capitalized on the benefits of wind power. Denmark was the first to install large off-shore wind farms, due to its limited suitable on-shore site locations and dense population.

The United Kingdom holds the next-highest position in the number of off-shore wind farms, producing 590MW of electricity.

TECHNIQUE

General: Wind energy is derived by harnessing the effects of the sun's thermodynamic heating of the planet. As the Earth is unevenly heated by the sun, warm air rises, while cooler air is drawn down to replace it. This heating-cooling cycle and the rotation of the planet create wind, which reaches from the Earth's surface up to the stratosphere.

The strongest winds are at higher altitudes, where continuous wind speeds of over 100 miles per hour may be found. As wind moves its mass, that motion becomes a source of energy. Windmills collect part of this wind energy by mechanically harnessing it to produce electricity. The production of electricity from a wind turbine depends on the size of its rotors and the wind speed. The production of energy is denoted in wattage, or watts, which is a small unit of power measurement. The output energy capacity of wind turbines and other conventional power plants is rated in watts. The term kilowatt, or kW, equals 1,000 watts. A megawatt (MW) is one million watts, and a gigawatt (GW) is one billion watts. According to the American Wind Energy Association (AWEA), when winds average 12 mph, a 10-kW turbine is able to produce 10,000kW; this amount of electricity fulfills the average annual need of a single American household. A 5-MW turbine can produce more than 15 million kWh in a year, or enough to power 1,400 American households.

Wind-farm created electricity may be transported through electrical lines to the national electric power network, called the "National Grid." Individual turbines are linked to one another through a power collection system; once electrical current arrives at a substation, it is increased in voltage by a transformer and sent to the Grid along high-voltage transmission towers. Any excess electricity generated by the wind farm may also be sold to the local utility company for a profit.

The term "small-scale windmill" is used to describe a structure that generates 50kW or less of electrical power; the term "wind turbine" describes a structure that generates 100kW or more.

Wind farms, or wind plants, refer to areas where numerous wind turbines are located; they are most commonly used to generate large amounts of energy for consumer use.

Wind turbines and windmills are mounted on a tower in order to capture the greatest wind speed. Towers are mostly tubular and made of steel or aluminum. The most efficient wind towers are at least 100 feet in height.

The industry standard calls for the bottom of a turbine's blades to be at least 30 feet above the top of any object situated within 500 feet. The larger the turbine, the higher the needed tower.

The wind industry states that an average annual wind speed greater than nine miles per hour is needed for small windmills. Utility-sized wind turbines need a minimum wind speed of 13 miles per hour in order to turn the rotor fast enough to generate electricity. Doubling the wind speed will increase the amount of generated power by a factor of eight; therefore, what is a small difference in wind speed makes a large difference in energy production. For this reason, the wind industry performs studies of average wind speeds in any projected wind farm site location.

Different styles and positions of rotor blades have been used throughout history. In modern turbines there are two basic styles for positioning the rotors: the vertical-axis, or egg-beater style, and the horizontal-axis, or propeller style. Horizontal-axis turbines and windmills are the styles most frequently in use today.

The rotors, or blades, are typically made of fiberglass-reinforced polyester. Wood epoxy blades are still used in some areas of the world. The diameter of a large off-shore rotor may be longer than 110 meters (360.89 feet). The rotors of smaller windmills are eight meters or less (26.24 feet). The size of turbine blades has been increasing over the years. In 1981, the average rotor blade size was 10 meters. In 2000, the average rotor blade size was 71 meters.

Most modern turbines use two or three blades per tower. The rotors of the turbine act like airplane wings. When the wind passes over the blades, the pressure on the downwind side of the blade pulls the blade, while the wind on the front part of the blade pushes. This wind action causes the rotors to turn in what is called "lift."

As the blades spin, they turn a shaft. Gears connect that shaft to a high-speed shaft: It increases the blades' rotational speed from 30-60 rotations per minute (rpm) to about 1,000-1,800rpm. This is the speed of rotation required by most generators to produce electricity.

Some systems in remote areas connect the turbine to a photovoltaic (solar) system for storing excess electricity, instead of connecting to a utility power grid.

One megawatt of wind power generates about as much electricity as250-300 U.S. households. The United States currently generates enough megawatts of electricity from wind to power seven million average American homes.

At the Earth's surface, different geographical locations have different wind speed distributions. Wind-speed consistency varies not only from site to site, but also from season to season and hour to hour. This element of wind energy is called wind density; it is calculated by relating the force of the wind to its elevation above the ground over a period of time. Color-coded wind maps are available for various regions of the United States and are used as an index called "NREL CLASS." The higher the class, the better suited a particular region is for installing a wind power turbine.

This variability in day-to-day and hour-to-hour wind strength and constancy poses the biggest challenge in effectively harnessing wind energy for mass electricity production; it is the focus of many current global research efforts. In Texas, for example, on hot summer days when air conditioning demand is high, that region experiences low-wind-speed weather patterns.

The primary goal of utility companies is to maintain enough power to meet any demand at any time of day, plus a reserve of power for unexpected peak periods. This goal makes the incorporation of wind power (which is often inconsistent) problematic.

To counteract the inherent performance drawback of wind power, wind plant experts have learned that distributing large-scale turbines over a broad area increases the chance that some of the turbines will be producing energy.

The actual total capacity of wind energy is a long-standing topic of much debate among global experts. Referred to as the "capacity factor," the issue stems from the gap between what a turbine may produce under ideal conditions, with constant steady winds year-round, to what it may actually produce under real-life conditions in the same time frame. Unlike traditional fuel sources, such as coal, gas, or nuclear fuel, wind power's capacity factor is inconsistent. Some experts, such as Battelle Pacific Northwest Laboratory, a federal research lab, cite wind power as having only a 20-40% true capacity, versus gas or coal's 100% energy production capacity (assuming both generator types are in top working order).

Earlier design problems, which limited the time the wind turbine was actually functioning and ready to produce electricity, reduced its earlier production/capacity figures. Modern turbines are much more reliable and "available" to produce electricity.

Complex capacity calculations are used to determine the baseline cost of wind energy's electricity production. To wind power's benefit, wind-created electricity is entirely free of cost, so that its total capacity is a true figure. In coal or gas-created electricity, however, fuel costs play an important role and reduce the true capacity factor. Using the cost of natural gas fuel in estimating its true capacity factor may lower its total capacity by 5-25%. Under high-gas-cost conditions, a gas turbine electrical plant may only be run at peak-power demand times, such as early mornings and evenings. Nuclear plants have a low fuel cost, which typically reflects an actual 90% capacity factor.

Wind farm planning focuses on two areas of development: land-based wind farms and off-shore wind farms. Within land-based farms can be found both large commercial facilities and small-scale residential or farm usage.

The United States and China lead the world in the development of onshore, land-based wind farms. Texas and California contain the most domestic wind farms, while the steppes of Xinjiang and Inner Mongolia in China contain the most Chinese wind farms.

Wind power currently provides almost 25% of electricity in Schleswig Holstein, a state in the north of Germany. In Denmark's western region, wind generates 100% of electricity produced in the winter season.

On-shore wind farms: In open flat land, a large-scale land plant requires about 60 acres per megawatt of electricity. Of this land, only 5% (three acres) is actually occupied by the wind turbines, access roads, and other out-buildings. The remainder of the land site may be used for farming or ranching. A ridgeline placement of a wind farm may use as little as two acres per megawatt.

Current limitations by manufacturers to provide larger and more productive turbines have slowed farm site installations. As the industry develops better techniques and materials for their systems (the rotor blades in particular), the current shortage of components should improve.

To date, a 50-MW land-based wind farm installation may be completed in a timeframe of 18 months to two years. In the United States, the plains of the Midwest are considered ideal site locations

In urban settings, little scientific study has been done in regard to turbine placement, wind patterns, and the effect of adjacent buildings or structures on the alteration of normal wind patterns. One study, conducted by the Carbon Trust in the United Kingdom, examined the electricity-generating potential of small turbines, and proposed that small systems could potentially provide up to 0.4% of the total U.K. electricity consumption. According to the authors, this could potentially prevent 0.6 million tons of carbon dioxide emissions.

Off-shore wind farms: Large off-shore turbine sites are favored by many wind experts due to the stronger, steady off-shore wind speeds and the ability to install larger turbines than on land. However, as water depth and wave height increases, the cost of installation also rises. While Europe has many shallow coastal areas suitable for off-shore wind farms, the United States has fewer shallow coastal regions to support large wind facilities. One of the largest proposed off-shore wind sites in the United States is off Cape Cod in Massachusetts.

Additional capital expenditures for large off-shore utility sites are needed to expand and maintain transmission lines from ocean sites to land-based substations.

THEORY/EVIDENCE

General: Experts around the world estimate that the total atmospheric wind power available to be harnessed is much greater than the world's current energy needs. The limit to the use of this endless energy source is set by economic, environmental, political, and regulatory constraints.

Inconsistent wind speeds over a 24/7 time period will decrease a plant's ability to adequately supply electricity to the National Grid. Experts are considering solutions to this problem by coupling wind systems with conventional backup systems, such as gas-burning generators, solar panel hybrid systems, or massive battery-storage units; these systems would hold reserve electrical supplies to be used when needed.

In the United States, it is estimated that to increase and retrofit the current grid transmission system to incorporate renewable energy sources would cost at least $60 billion.

Of all electrical production resources, only wind and hydroelectric generation have minimal fuel costs and long-term maintenance requirements. When estimating the potential return on investment, the initial cost of construction of the turbine and transmission facilities, construction loans, return to investors, and estimated annual production levels are averaged over the projected 20-30 years of the equipment's useful life.

In 2006, the British Wind Energy Association reported that the average generation cost of on-shore wind power was comparable to the same cost for coal or gas production. As the resource costs of gas, coal, and oil increase, however, the comparative costs of wind power generation decrease. The industry's approach is to install as large a power-producing turbine as possible; this approach makes use of the same installation and transmission line improvement costs as do smaller and less productive turbines. For this reason, the unlimited space availability of off-shore systems becomes attractive.

The commercial usage of wind power also depends on the pricing structure used for large power producers. Electricity prices are regulated throughout the world and may not give wind power a competitive edge. Despite wind power's "clean" energy, the issues surrounding the use of wind power may not attract needed financial investors, who look for consistent and dependable returns with low risk.

Countries such as Canada and Germany provide financial incentives for wind turbine construction, thereby attracting investors. These countries have created tax credits for construction costs, for minimum purchase prices for wind generated electricity, and for assured grid access; these tax credits are called "feed-in tariffs." The United States has had tax credit incentives for wind farm construction, especially during the 1980s; however, start-up wind farm owners have seen many of these benefits disappear as public and political support shifts.

On-shore wind farms: The placement of land-based wind farms must contend with roadway obstructions, populated areas, and geographical obstructions.

Off-shore wind farms: Off-shore wind farms are viewed by many experts as the most cost-effective site location for the United States. Benefiting from on-going wind speeds and no geographical barriers such as mountains, off-shore locations are able to support unlimited rotor size; furthermore, the components may be easily transported over water to the construction site. While the construction and maintenance of off-shore turbines is more expensive than that of land-based turbines, the increased size of the rotors and their efficiency in electricity generation may offset these factors.

In the United States, the Coast Guard is the regulating body for off-shore wind plant markings, lighting, and fog signal alert systems. They are actively involved in site planning for any shallow or deep water projects.

Current Danish studies suggest that the small area of seabed that is required to support a wind turbine has little impact on the ocean floor or on marine inhabitants. Many environmental groups have stated that ocean wind farms may provide additional safe-spawning sites, as well as protection from fishing endeavors.

Potential advantages: Wind is a clean, renewable fuel source. Wind energy does not pollute land, air, or water.

No greenhouse gases are emitted during the production of wind-based electricity.

Wind is a domestic resource that is not subject to political or national conflicts.

Wind energy is one of the lowest priced energy sources available using current technologies. Once a wind system is installed, there are no fuel costs.

The use of wind energy would reduce the drain on natural gas resources and would potentially reduce the subsequent costs. Projections by the Department of Energy estimate that wind power would provide a savings of 12% over natural gas prices, which is the equivalent of saving consumers over $130 billion.

Maintenance requirements of a wind plant over the average 20-year life span of the system are low.

Minimal water is used during the production of wind energy. According to the California Energy Commission's 1995 data, water usage from wind energy is minimal: It is used only for rotor blade cleaning in desert climates and to remove insects. Compared to the large amount of water needed to cool and process nuclear (0.62 gallons/kWh), coal (0.49 gallons/kWh), and oil (0.25 gallons/kWh) energy sources, wind uses virtually no water (0.001 gallons/kWh).

According to the U.S. Department of Energy's Wind and Hydropower Technologies Program report, wind power has the potential to reduce the electric industry's use of water by four trillion gallons from 2007 through 2030. In the Southwestern part of the United States, where water shortages are increasing, wind speeds and flat open areas are optimal for wind farm sites. Wind could provide an economical way for these areas to meet their energy needs without increasing their demand on water resources.

The wind manufacturing industry could create more than 30,000 new jobs in the United States.

Land lease arrangements with local landowners and local tax municipalities could potentially generate in excess of $1 trillion in economic activity related to electrical production from wind power.

Potential disadvantages: Many potential sites for wind farms are far away from populated areas that need electricity. New transmission lines, substation management sites, and interconnection with national grid lines would have to be designed and installed. Initial investment costs are substantially higher than those of fossil-fueled generator systems.

Electricity generation and consumer use must stay in balance over a 24-hour timeframe; wind power production, however, cannot be increased just because consumer needs increase. The American Wind Energy Association (AWEA) proposes a solution; it estimates that only about 2MW of conventional electrical generation is necessary to compensate for intermittent wind availability at a100-MW wind plant.

Some critics claim that the manufacturing of wind turbines and their towers consumes resources. Steel, concrete, aluminum, and high-strength resins are all used in the construction of a wind turbine. In addition, the transport and installation of a wind system requires gasoline and oil, and the process also emits greenhouse gases. The British Wind Energy Association's study on the impact of the manufacture and delivery of a wind turbine showed that the cost of construction is repaid within a three to five month period, through savings in the turbine's energy production. A report to the British House of Lords indicated a 1.1 year time frame for payback onshore sites. Off-shore sites (with their higher production rates) boast an even shorter payback time, despite their increased installation costs.

One argument against wind power is that public subsidies are being used for a method that will have limited impact on national electricity production needs. This has been a major detracting argument in the United States.

Earlier American wind turbine design flaws have and are being addressed to provide real competitive placement in the worldwide turbine manufacturing industry; Danish turbine sales, however, still hold over 50% of the U.S. wind farm market

Environmental disruptions may occur when turbine sites disturb hard-packed soil areas, such as desert locations; long, high mountain ridgeline locations, such as in the New England area, may also be troublesome. Techniques borrowed from the skiing industry for protection of the environment are expected to prevent erosion problems with wind farm construction.

Newer technologies for rotor blades and their housings have made turbines extremely resistant to storm-related high wind speeds. In a storm, rotor blades are designed to turn out of the wind and slow down whenever wind speeds reach 50 miles per hour or more.

Some naturalists have voiced concern that wind farm sites might negatively impact wildlife habitats. Research has shown that about one bird is killed per turbine per year on land-based wind farms in the United Kingdom. In contrast, about 10 million birds are killed annually by collisions with cars, and 1 billion birds are killed by house cats. The Audubon Society is in support of wind energy; however, the wind farm at the Altamont Pass in California has seen elevated deaths in raptors that inhabit the area. A proposal has been made to restrict construction of wind farms in sites which support threatened or endangered bird species.

For an unknown reason, migratory bats seem to have a higher death rate through mishaps with large turbine rotor blades. Bat species such as the hoary bat, red bat, and the silver-haired bat appear to be the most at risk in North America. The cause of this phenomenon is being researched through a collaboration between the U.S. Department of Energy's National Renewable Energy Laboratory and Bat Conservation International; their efforts are collectively known as the "Bats and Wind Energy Cooperative" (BWEC).

The health of coral reefs and marine fish has been raised as a concern in relation to off-shore wind farms. Studies are underway to determine the impact of tower noise or vibration on marine life, particularly on whales. Most towers have a small ecological footprint, even in the larger turbine sizes. Danish studies have shown that the impact of tower construction on the ocean floor is minimal, with the duration of construction being about six months. The AWEA suggests that more study is needed to understand the impact of a wind tower on local fauna.

Local communities may have zoning restrictions on the maximum permitted height of a tower, on the distance from the edge of the property (called the setback), and on the need for soil tests to determine a site's ability to support the structure. Some zoning boards have existing policies that cover turbine permits; others do not, and the interested party must provide all technical documentation. This process may become time and money intensive.

Insurance companies, which typically insure a home's structure, may cover a wind turbine if it is listed as an "appurtenant" or uninhabited structure. Some insurance companies are now requiring a separate policy for wind turbine systems.

The possibility of noise pollution has been cited by critics of wind energy. However, modern improvements in rotor blade shape, with thinner blade edges and lighter component materials, have greatly reduced noise levels during use. The setback requirement has also helped to alleviate this problem. Rotor designers now claim that rotor noise is no louder at 300 meters (984.25 feet) than it is in the reading room of a library.

Visual aesthetics may also be a concern: The Massachusetts Cape Wind farm was delayed for years over this issue. As manufacturers have streamlined the strength and shape of the materials used in construction, the visual impact of these structures has decreased. Wind plants now place towers in a uniform spacing pattern, and if possible, away from a person's line of sight. Denmark claims that their wind farms have become tourist attractions. Advocates of off-shore wind farms argue that it is possible to install ocean farms in outlying deep waters, so that they are not visible from land.

As oil and gas prices climb, some companies have been using unethical methods to market scaled-down windmill systems (such as rooftop wind turbines) to homeowners; these companies have been making unsubstantiated claims of both economic savings and unrealistic levels of energy production. Marketing materials state that these home-based systems are able to lower the electricity bills of homeowners, and that the systems are able to power homes during extended utility outages; these companies also claim that rooftop wind systems may help homeowners avoid the high costs of routing electricity to remote locations. Such marketing claims are the subjects of concern. Even the Massachusetts Small Wind Report of 2008 cautions that their group's testing of small wind systems has "shown less than one-third of the average production projected by the installers." One tested turbine was shown to generate only a 1% average capacity factor.

Although there has been some concern that wind turbines could interfere with the radar of ships and airplanes, these claims have been unfounded. Even though radar is built to focus on moving objects, it is possible to adjust radar systems to ignore the movement of wind farm rotors. According to experts in the field, however, more investigation is needed before any wind plants are constructed near airports or military bases.

Financial considerations: According to the AWEA, wind power has one of the shortest pay-back times of any energy technology: It usually takes about three to eight months for a wind turbine to replace the energy that was used to create, install, operate, and (eventually) retire it.

The return on investment for off-shore sites is even shorter than that of land plants; in spite of their higher installation costs, off-shore sites boast a higher electricity production rate.

When comparing natural gas to wind power, research has shown that initial construction costs are higher with wind farms; however, the on-going fuel cost of natural gas is greater than that of wind and is subject to a projected decreasing supply. In comparison to oil-generated electricity, wind is a domestic resource not subject to price fluctuations. Nuclear power has had a long history of public concern and disapproval, with site location and waste disposal continuing to be problematic in many regions of the world.

Modern utility wind plants are now able to generate electricity at a price that is 80% less than twenty years ago.

A 2005 study by the New York State electric system found that adding 10% of wind generation to their network provided a reduction of $305 million in one year in consumer payments for electricity.

There are three major factors in the costs of electricity generation on wind farms: the number of turbines at a site, the average wind speed at that site, and the cost of installing the turbines. Financial returns are higher when wind farms are situated in places with stronger winds, when more turbines are available to capture the wind, and when there is less cost associated with constructing the site. If a wind farm is located off-shore, the expense of transmitting electricity to land will increase the costs involved, and lower the return on investment.

When comparing the costs involved with wind systems to those of traditional energy production methods, many experts fail to include indirect costs. A major European Union report states that most comparisons of energy generation costs do not adequately reflect the true costs of that production. For example, in the last 30 years the U.S. federal government has paid more than $35 billion to cover the medical costs of coal miners who developed black lung disease. In addition, unknown numbers of adults and children need frequent medical treatment due to air pollution-related respiratory disorders, caused by the burning of coal.

Insurance companies initially refused to accept the risk of covering nuclear power plants. As a result, the federal government has pledged to act as the "insurer of last resort" if claims exceed the insurance industry's limit.

The U.S. government is also paying for the ongoing military protection of oil shipment lanes in the Persian Gulf; that factor is not calculated into the cost of oil-based electricity generation.

Wind and solar development and production are now considered to be the largest potential sources of manufacturing jobs available worldwide in the 21st Century. Wind turbine maintenance crews will also be needed and will serve as another industry employment option.

For rural communities, wind farms could become a viable avenue for income. Steady income derived from landowners' lease or royalty agreements with utility companies is increasing. Using 2005 data, an estimate of the income created for a landowner by leasing a single turbine site to an electricity-generating wind facility is $3,000 per year. A 250-acre farm with a lease agreement for a two- to three-acre wind farm site could generate $14,000 in yearly income. European sites traditionally grow crops and farm cattle immediately adjacent to wind turbine towers without ill effect.

To encourage wind energy expansion, in 2008 the U.S. government enacted an up-front tax credit, available through December 2016, to help consumers purchase small wind systems.

Funded by the Department of Energy's Wind Energy Program, Sandia National Laboratories is conducting applied wind energy research to increase the practicality and efficiency of wind turbines.

One comprehensive federal proposal, called "20% Wind Energy by 2030," is aimed at providing a structured method to incorporate wind energy into the National Grid.

If wind energy is accepted into the national composite of electricity generation, the way that producers are paid and how that payment is calculated will need to be revamped. Much discussion has been given to restructuring the utility industry. One suggestion is to create a "Renewables Portfolio Standard": Each company that generates electricity in the United States would be required to obtain part of its energy supply from a renewable energy source.

A possible alternative to the Renewables Portfolio Standard would require utilities that do not create their own renewable energy to buy credits and trade them toward a set number of units. This credit-trading approach has been used by the federal Clean Air Act in regards to pollution requirements. At least 20 states are considering this method of energy management.

Some regions are also considering the creation of a "green payment schedule" for consumers. In some of these arrangements, homeowners would contract with a utility company to purchase a specified yearly amount of "green-produced" energy. Currently this purchase price is slightly higher than traditional energy resources; however, this process secures a market for the utility company, it encourages companies to consider refurbishing their plants, and it provides the homeowner with a fixed energy price for that year. In other arrangements, a complex "green tag certificate" is bartered by traditional utility companies with producers of renewable energy. At present, no single approach has solved the intricate problems of restructuring a long-standing network.

The future effect of payment methods and government incentives for wind power at the utility-scale and the independent small-user level is currently unclear.

HEALTH IMPACT/SAFETY

General: The production of wind power does not create air or water emissions or hazardous waste. Traditional fossil fuel power plants, however, emit sulfur dioxide, nitrogen oxide, carbon dioxide, and particulate airborne matter.

The American Wind Energy Association (AWEA) estimates that if the United States were to generate 24 billion kilowatt-hours of electricity by wind, it would prevent 30 billion pounds of carbon dioxide, 76,000 tons of sulfur dioxide, and 36,000 tons of nitrogen oxide from being released into the atmosphere

Sulfur dioxide, which is produced by traditional electrical generator plants, has been linked to acid rain, which is harmful to forests, water reservoirs, and wildlife. Acid rain may also corrode buildings and bridge structures.

Nitrogen oxide, released by the burning of natural gas, contributes to smog and is a health risk.

Carbon dioxide is a "greenhouse gas," which contributes to global warming, to the changing of weather patterns, and to the creation of droughts and floods; furthermore, it negatively impacts human health.

Particulate matter emissions from traditional energy generators have been closely linked to an increase in respiratory diseases, such as asthma and lung cancer.

The federal government has paid out more than $35 billion over the past 30 years to cover the medical costs of coal miners suffering from black lung disease. Currently, unknown numbers of adults and children need frequent medical treatment due to respiratory disorders that are caused by air pollution. Wind energy is free of these negative impacts on human health.

Wind energy does not pollute water during operation as do nuclear power plants.

In the 20 years of operation of wind plants in Europe, only one human fatality has been recorded. This casualty occurred when a skydiver went off-course into a wind plant.

Some naturalists have voiced concern that a wind farm's site negatively impacts wildlife habitats. Research in the United Kingdom has found that about one bird is killed per turbine per year at land-based wind farms. In the same country about 10 million birds are killed annually by collisions with cars and 1 billion birds are killed by house cats. The Audubon Society supports wind energy; however, the wind farm at the Altamont Pass in California has seen a rise in the death rate of raptors that inhabit the area. A proposal has been made to restrict the construction of wind farms in sites that support threatened or endangered bird species.

Migratory bats seem to have a higher death rate through mishaps with the large rotor blades found on wind farms; the reason for this situation is still unknown. Bat species such as the hoary bat, red bat, and the silver-haired bat appear to be the most at risk in North America. The cause of this phenomenon is being researched through a collaboration between the U.S. Department of Energy's National Renewable Energy Laboratory and Bat Conservation International; their efforts are collectively known as the "Bats and Wind Energy Cooperative" (BWEC).

The health of coral reefs and marine fish has been raised as a concern with off-shore wind farms. Studies are underway to determine the impact of noise or vibration of wind towers on marine life, particularly on whales. Most wind towers have a small ecological footprint, even when their turbines are large. Danish studies have shown that a tower's impact on the ocean floor is minimal, and that the duration of tower construction is about six months. The AWEA suggests that more study is required to understand a site's impact on the local fauna.

On-shore wind farms: Earlier problems with injuries from ice that accumulates on rotor blades and is "thrown" have been eliminated by new blade designs.

Concern over "stray voltage" problems with turbines has been eased: Previous stray voltage issues resulted from faults in wiring, and were not due to the wind turbines themselves. The proper installation, use, and maintenance of electrical components should prevent the transfer of stray electrical current outside of the plant's system.

The impact of wind farms on geographical sites and on wildlife movement patterns is a current area of research interest.

Off-shore wind farms: Interagency collaboration is beginning to occur between plant design engineers and environmental groups, in order to maintain the health of off-shore wind farm sites.

FUTURE RESEARCH OR APPLICATIONS

General: Research throughout the world suggests that there is 70-80% support by the general public for wind power installations.

States that are developing wind farms for commercial use include Alaska, Hawaii, Idaho, Maine, Michigan, Nevada, Tennessee, Vermont, and West Virginia.

Wind may eventually provide electricity to developing nations; almost two billion people in developing countries currently live without electricity.

Over the past five years, Denmark's western region has been able to meet over 100% of the area's electrical demands in winter through the use of wind power. Denmark is continuing its wind expansion program.

The U.S. Department of Energy (DOE) has recently started a project to study whether wind and hydropower could be combined to provide a consistent supply of electricity. Researchers feel that wind (when available) could provide energy and that hydropower could act as a "storage battery," for times when wind is not active. Experts anticipate that this research will be a long-term project.

According the American Wind Energy Association (AWEA), wind energy usage in the U.S. National Grid may require a consistent governmental policy approach and support for long-term research, manufacture, and installation. Tax credits, incentive plans, and feed-in tariffs are part of this process.

Nondiscriminatory access to transmission lines must be available to wind energy producers.

Traditional energy producers are typically charged a penalty fee if they are unable to supply electricity when scheduled. With wind's inherent intermittent behavior, new policies for wind energy production will need to be implemented within the industry.

New transmission lines and substations will have to be constructed to augment the current national grid. Areas which have been historically underserved, such as areas west of the Mississippi River, will need to be provided with access to grid-based electricity.

Companies that connect to new high-voltage transmission lines need to be sensitive to population density, environmental concerns, and cost elements.

Off-shore wind farms: One new theory of off-shore site placement for the future is the construction of floating platforms at sea. At sea, the increased wind speeds and freedom from geographical limitations on size may improve energy-generation capacities. Floating platforms would eliminate any impact that a wind plant's structure might have on ocean sea beds and coral reefs. Researchers are developing warning devices that would alert ships to the presence of these floating platforms in poor visibility conditions.

On-shore wind farms: The U.S. Department of Energy's Wind Energy Program's Distributed Wind Technology research is working to improve small turbines up to one megawatt for farms, ranches, small industry, and remote developing areas. Its goal is to expand the number of small installed wind turbines from 2,400 turbines in 2007 to five times that number. Research is focused on independent testing for safety and on the performance of current manufacturers' products; it is also hoping to encourage the development of subcontractors' prototypes, in order to expand the efficiency and reliability of these smaller units.

"Green Power" interest, launched in the 1990s, has developed initiatives for all renewable sources, such as solar power, geothermal options, biomass, and hydropower. In Colorado and Texas, the focus has been on harnessing wind power. Some wind farms in California are considering refurbishing their older turbines. As political concerns increase over the availability of fossil fuels in the future, a renewed sense of effort has begun in the wind energy industry.

For investors, wind power could be an appealing option. The large international market for smaller windmills for individual and village use is essentially untapped.

Wind and solar development and production are now considered to be the largest potential sources of manufacturing jobs available worldwide for the 21st Century.

Mechanical engineers and wind experts are experimenting with ways to reduce the weight of the rotational shafts and gear boxes with "direct-drive" generators. These newer generator designs may be able to operate in lower wind speed conditions, opening up vast areas of potential wind farm sites.

Research into increasing the blade capture of wind energy by 5-10% is underway at Sandia National Laboratories. For example, the Sweep Twist Adaptive Rotor blade features a curved tip that is able to function in a much lower wind speed environment.

A turbine generator housing that is able to "nod" up and down in relation to wind turbulence is another recent innovation; it should help to prevent damage to generator housings in gusting winds.

Since current storage technology is inadequate for holding excess wind-generated electricity, manufacturers are working on the improvement of battery storage systems.

A federal proposal called "20% Wind Energy by 2030," sponsored by the U.S. Department of Energy (DOE), is aimed at providing a structured method to incorporate wind energy into the National Grid. The proposal is a collaborative effort between more than 100 governmental, utility, and private manufacturers. In their report, one possible scenario of reaching 20% wind energy by 2030 is contrasted to a situation where no new wind power is installed. Projections are based on the assumption that U.S. energy needs may increase by 39% between 2005 and 2030; it also assumes that the supply of wind power may increase by 15% by that end date. In addition, there is an assumption that current technology will be utilized, and that overall turbine costs will decrease by 10%.

The DOE's projection includes the use of onshore, shallow off-shore, and deep off-shore site locations, with 46 states having substantial on-land wind development by 2030. Four states, Louisiana, Mississippi, Arkansas, and Connecticut would not have substantial wind farms due to various geographical constraints. Off-shore sites would run from Oregon down the California coast, as well as from Maine down the East coast to Florida. The need to expand grid transmission lines would be concentrated in the Midwest, west of the Mississippi River, and through the upper Northwest region. The economic costs of the 20% wind goal, using 2006 dollars, show a "2% investment difference between 20% wind and no new wind" scenario. This cost difference is the equivalent of an additional 50-cent per month increase in the electricity costs of an average U.S. household. Natural gas consumption would decrease by 50%; oil consumption would decrease by 11%; and coal consumption would decrease by 18%. Furthermore, expanded use of wind power would prevent the need for construction of new 80GW coal-burning power plants.

With this agenda, the price stability of energy production would be a potential benefit for Americans. Carbon dioxide air emissions would be lowered by an estimated 825 million metric tons per year; acidification of lakes and streams would be decreased; mercury and other airborne pollutants would be reduced; and 4 trillion gallons of water would not be needed for electric production. The total amount of "footprint" land area impacted by this goal would be about 618,000 acres, which is an area less than the size of Anchorage, Alaska. The report found that affordable, accessible wind resources are available in the United States; that needed raw materials to construct additional wind farms are available; and that current transmission abilities, mostly in remote areas, are the limiting factor. The report calls for improvements in technology, environmental impact studies, the development of siting and transmission strategies, and increased governmental support for manufacturing, job placement, and regulatory formats for localities.

International groups within the wind energy industry are joining together to share research data. Optimism is high that major, upcoming technological breakthroughs could place wind power on an equal footing with traditional power resources.

Renewed public interest has given support to wind energy as political conflicts, economic shifts in oil pricing, and governmental financial supports change.

AUTHOR INFORMATION

This information has been edited and peer-reviewed by contributors to the Natural Standard Research Collaboration (www.naturalstandard.com).

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