Wind power in the United States is a branch of the energy industry that has expanded quickly over the latest several years.For calendar year 2016, wind power in the United States amounted to 226.5 terawatt-hours, or 5.55% of all generated electrical energy.
As of January 2017, the U.S. nameplate generating capacity for wind power was 82,183 megawatts (MW). This capacity is exceeded only by China and the European Union. Thus far, wind power's largest growth in capacity was in 2012, when 11,895 MW of wind power was installed, representing 26.5% of new power capacity.
In 2016, Nebraska became the eighteenth state to have installed over 1,000 MW of wind power capacity.Texas, with over 20,000 MW of capacity, had the most installed wind power capacity of any U.S. state at the end of 2016. Texas also had more under construction than any other state currently has installed. The state generating the highest percentage of energy from wind power is Iowa.North Dakota has the most per capita wind generation. The Alta Wind Energy Center in California is the largest wind farm in the United States with a capacity of 1548 MW. GE Energy is the largest domestic wind turbine manufacturer.
The first municipal use of multiple wind-electric turbines in the USA may have been a five turbine system in Pettibone, North Dakota in 1940. These were commercial Wincharger units on guyed towers.
In 1980 the world's first wind farm, consisting of twenty 30 kW wind turbines was installed at Crotched Mountain, in New Hampshire.
From 1974 through the mid-1980s the United States government worked with industry to advance the technology and enable large commercial wind turbines. A series of NASA wind turbines were developed under a program to create a utility-scale wind turbine industry in the U.S., with funding from the National Science Foundation and later the United States Department of Energy (DOE). A total of 13 experimental wind turbines were put into operation, in four major wind turbine designs. This research and development program pioneered many of the multi-megawatt turbine technologies in use today, including: steel tube towers, variable-speed generators, composite blade materials, partial-span pitch control, as well as aerodynamic, structural, and acoustic engineering design capabilities.
Later, in the 1980s, California provided tax rebates for wind power. These rebates funded the first major use of wind power for utility electric power. These machines, gathered in large wind parks such as at Altamont Pass would be considered small and un-economic by modern wind power development standards. In 1985 half of the world's wind energy was generated at Altamont Pass. By the end of 1986 about 6,700 wind turbines, mostly less than 100 kW, had been installed at Altamont, at a cost of about $1 billion, and generated about 550 million kWh/year.
The U.S., as of 2017, has over 82 GW of installed wind power capacity. Only China has more installed capacity.
The five states with the most wind capacity installed at the start of 2017 were:
. Texas (20,321 MW)
. Iowa (6,917 MW)
. Oklahoma (6,645 MW)
. California (5,662 MW)
. Kansas (4,451 MW)
Fourteen states now have 10 percent or more of their generation coming from wind power. Most of these are in the central plains. These states include North Dakota, South Dakota, Minnesota, Iowa, Nebraska, Colorado, Kansas, Oklahoma, New Mexico, Texas, Maine, Vermont, Oregon, and Idaho.
The top five states according to percentage of generation by wind in 2016 were:
. Iowa (36.6%)
. South Dakota (30.3%)
. Kansas (29.6%)
. Oklahoma (25.1%)
. North Dakota (21.5%)
A 2012 report by a clean energy consulting group concluded that new wind farms can produce electric power in the 5-8 cents per kWh range, making wind power cost-competitive with fossil fuels in many areas. As of 2013, the US Energy Information Administration estimates the "levelized cost" of wind energy from new installations as 7 to 10 cents per kWh, depending on the geographic area, but cautioned that levelized costs of non-dispatchable sources such as wind should be compared to the avoided energy cost rather than the levelized cost of dispatchable sources such as natural gas, or baseload sources such as coal or geothermal.page needed] In 2015, a Koch-funded institute of Utah State University stated that the cost of wind energy is higher than most cost estimates calculate. Renewable portfolio standards require renewable energy to exist (most of them intermittent such as wind and solar), but at the expense of utilities and consumers. The production tax credit makes wind power cheaper for utilities and consumers, but at the expense of taxpayers.The American Wind Energy Association has criticized the study of lacking comparison with pollution and subsidies incurred by other electric power sources, and for counting transmission as a cost rather than a benefit.
Wind power has increased dramatically over the past years. In 2010, however, newly installed generating capacity was about half of the previous year due to various factors, including the financial crisis, and recession. In 2013 there was a 92% reduction in newly installed generating capacity compared to 2012, due to the late extension of the PTC The graph at left shows the growth in installed wind generation capacity in the United States based on data from the Office of Energy Efficiency and Renewable Energy. In 2008, installed capacity in the U.S. increased by 50% over the prior year. The world average growth rate that year was 28.8%.
By 2014, the wind industry in the USA was able to produce more power at lower cost by using taller wind turbines with longer blades, capturing the faster winds at higher elevations. This opened up new opportunities and in Indiana, Michigan, and Ohio, the price of power from wind turbines built 300 feet to 400 feet above the ground competed with conventional fossil fuels like coal. Prices had fallen to about 4 cents per kilowatt-hour in some cases and utilities had been increasing the amount of wind energy in their portfolio, saying it is their cheapest option. For power contracts made in the year 2014, the average price of wind power fell to 2.5¢/kWh.
The capacity factor is the ratio of power actually produced divided by the nameplate capacity of the turbines. The overall average capacity factor for wind generation in the US increased from 31.7% in 2008, to 32.3% in 2013.
Wind generation potential
According to the National Renewable Energy Laboratory, the contiguous United States has the potential for 10,459 GW of onshore wind power. The capacity could generate 37 petawatt-hours (PW·h) annually, an amount nine times larger than current total U.S. electricity consumption.The U.S. also has large wind resources in Alaska, and Hawaii.
In addition to the large onshore wind resources, the U.S. has large offshore wind power potential, with another NREL report released in September 2010 showing that the U.S. has 4,150 GW of potential offshore wind power nameplate capacity, an amount 4 times that of the country's 2008 installed capacity from all sources, of 1,010 GW.
The U.S. Department of Energy’s 2008 report 20% Wind Energy by 2030 envisioned that wind power could supply 20% of all U.S. electric power, which included a contribution of 4% to the nation’s total electric power from offshore wind power. In order to achieve this, however, significant advances in cost, performance and reliability are needed, based on a 2011 report from a coalition of researchers from universities, industry, and government, supported by the Atkinson Center for a Sustainable Future. Obtaining 20% from wind requires about 305 GW of wind turbines, an increase of 16 GW/year after 2018, or an average increase of 14.6%/year, and transmission line improvements. Analysts estimate around 25 GW of added US wind power in 2016-18, depending on the Clean Power Plan and PTC extensions. After the current PTC phase-out in 2021, additional wind power capacity is expected to be around 5 GW per year.
In 2015, electric power generation from wind power was 10 percent or more in twelve U.S. states: Colorado, Idaho, Iowa, Kansas, Maine, Minnesota, North Dakota, Oklahoma, Oregon, and South Dakota, Vermont, and Texas. Iowa, South Dakota, and Kansas each had more than 20 percent of their electric power generation come from wind. Twenty states now have more than five percent of their generation coming from wind.
In 2016 Texas surpassed the 20,000 MW mark by adding over 1800 MW of generating capacity. In 2011, Texas had become the first state to surpass the 10,000 MW mark.
In July 2008, Texas approved a $4.93 billion expansion of the state's electric grid to bring wind energy to its major cities from western areas of the state. Transmission companies will recoup the cost of constructing the new power lines, expected to be completed in 2013, from fees estimated at $4 per month for residential customers. A lack of transmission capacity forced wind turbines to be shut down at times and reduced wind power generation in Texas by 17% in 2009.
The Roscoe Wind Farm in Roscoe, Texas, Texas's largest wind farm with 627 wind turbines and a total installed capacity of 781.5 MW, surpassed the nearby 735.5 MW Horse Hollow Wind Energy Center. It is located about 200 miles (320 km) west of Fort Worth and the wind farm area spans parts of four Texas counties.
Wind power in California has doubled in capacity since 2002. With a total of nearly 4,000 megawatts installed, as of the end of 2011, wind energy now supplies about 5% of California’s total electric power needs, or enough to power more than 400,000 households. The amount varies greatly from day to day. In 2011, 921.3 megawatts were installed. Most of that activity occurred in the Tehachapi area of Kern County, with some big projects in Solano, Contra Costa and Riverside counties as well. After 2014, California ranked second nationwide in terms of capacity, behind Texas with a capacity of 5,917 MW.
Large portions of California's wind output, are located in three primary regions: Altamont Pass Wind Farm (east of San Francisco); Tehachapi Pass Wind Farm (south east of Bakersfield), and San Gorgonio Pass Wind Farm (near Palm Springs, east of Los Angeles). The giant new Alta Wind Energy Center, is also located within the Tehachapi Pass region.
More than 35 percent of the electric power generated in Iowa now comes from wind power.Iowa had over 6900 megawatts (MW) of generation capacity at the end of 2016. Electrical energy generated in Iowa by wind in 2014 amounted to over 16 million Megawatt-hours. Since Iowa adopted a renewable energy standard in 1983, the wind power industry has generated over $10 billion in investment. The second concrete wind turbine tower to be built in the U.S., and also the country's tallest (377 feet) at the time built, is in Adams county. The tower was completed in the spring of 2016.
Oklahoma has one of the best resources in the United States. Bergey Windpower, a leading manufacturer of small wind turbines is located in Oklahoma. Programs leading to careers in the wind power industry are provided at tech schools, community colleges and universities in Oklahoma. The Oklahoma Wind Power Initiative supports the development of wind power in the state.
Wind power has been supported by a renewable portfolio standard, passed in 2007, and strengthened in 2009, which requires 10% renewable energy from electric companies by 2010 and 25% by 2025. Illinois has the potential for installing up to an estimated 249,882 MW of wind generation capacity at a hub height of 80 meters.
In 2012, Kansas saw a large number of wind projects completed making it among the largest and fastest growing wind energy markets. At the end of 2014 the total capacity sits at 2,967 MW. Kansas has high potential capacity for wind power, second behind Texas. The most recent estimates are that Kansas has a potential for 950 GW of wind power capacity. Kansas could generate 3,900 TW·h of electric power each year, which represents more than all the electric power generated from coal, natural gas and nuclear combined in the United States in 2011.
Wind energy meteorology
Winds in the Central plains region of the U.S. are variable on both short (minutes) and long (days) time scales. Variations in wind speed result in variations in power output from wind farms, which poses difficulties incorporating wind power into an integrated power system. Wind turbines are driven by boundary layer winds, those that occur near the surface of the earth, at around 300 feet. Boundary layer winds are controlled by wind in the higher free atmosphere and have turbulence due to interaction with surface features such as trees, hills, and buildings. Short term or high frequency variations are due to this turbulence in the boundary layer.
Long term variations are due to the passage of transient waves in the atmosphere, with a characteristic time scale of several days. The transient waves that influence wind in the Central U.S. are large scale and this results in the power output from wind farms in the region being somewhat correlated and not entirely independent. Large scale distribution of wind farms significantly reduce short term variability, limiting the relative standard deviation of the capacity factor to about 45%. The correlation is highest in summer and lowest in winter.
The US federal government has jurisdiction to prevent bird and bat deaths by wind turbines, under the Endangered Species Act, the Migratory Bird Treaty Act, and the Bald and Golden Eagle Protection Act. Under the 2009 Bald and Golden Eagle Protection Act, the Interior Department could issue permits to allow "non-purposeful take" for activities where eagle deaths were considered unavoidable; however, as of December 2013, no take permits had been issued to wind energy developers.
The United States Fish and Wildlife Service has published voluntary guidelines for design and siting of wind turbines to minimize bird and bat deaths. Interim guidelines were published in 2003, and the latest version in 2012. The document recognizes that even the best management practices may not prevent wind turbine bird deaths in violation of federal law, but stated: “However, if a violation occurs the Service will consider a developer’s documented efforts to communicate with the Service and adhere to the Guidelines.”
In 2013, the Obama administration was accused of having a double standard to protect the wind industry from Bald and Golden Eagle Protection Act prosecutions, while vigorously pursuing violations by oil companies and owners of power lines. The administration refused to divulge the number of raptor deaths reported to it by wind companies, saying that to do so would reveal trade secrets. The government also ordered federal law enforcement field agents not to pursue bird-death prosecutions against wind companies without prior approval from Washington. The policy was said to be an environmental trade-off to promote renewable energy.
In November 2013, the federal government obtained its first criminal conviction of a wind power operator for killing protected birds in violation of the 1918 Migratory Bird Treaty Act. Duke Energy plead guilty, and was fined $1 million, for the deaths of 160 birds, including 14 golden eagles, at two wind farms in Wyoming. The Justice Department charged that Duke had designed and sited the turbines knowing that they would kill birds; Duke noted that it had self-reported the bird deaths, and that US Fish and Wildlife Service guidelines for reducing bird deaths by wind turbines had not been issued when the turbines were built. After they were charged, Duke implemented a radar detection system, at a cost of $600,000 per year, designed to turn off turbines when approached by large birds; the company noted that the system was working, as no golden eagle deaths had been observed in more than a year of operation since the radar was installed.
In December 2013 the US Fish and Wildlife Service announced that it would issue 30-year permits to wind energy projects to allow for eagle deaths; previously, permits had been available for only 5 years, but none were issued to wind projects. Under the 30-year permits, wind power developers would be required to report eagle deaths, and the permits would be reviewed every 5 years. The measure was intended to remove what was seen as legal uncertainty discouraging wind energy investments. The government said that an environmental review was not needed for the change, because it was only an administrative change.The new regulation was welcomed by the American Wind Energy Association, which said that wind power caused less than two percent of human-caused eagle fatalities, and pointed out that the rules would require extensive mitigation and monitoring of eagle deaths.The extension of eagle taking permits from 5 to 30 years was opposed by a number of conservation groups, including the American Bird Conservancy, the Nature Conservancy, the Sierra Club, the Audubon Society, and the Humane Society of the United States.