Everything about wind power

What is a wind turbine and how does it work?				Wind energy and the economy

A wind energy system transforms the kinetic				What does the U.S. wind industry contribute
energy of the wind into mechanical or				to the economy?
electrical energy that can be harnessed for
practical use. Mechanical energy is most				Wind power supplies affordable, inexhaustible
commonly used for pumping water in rural or				energy to the economy. It also provides jobs
remote locations. Wind electric turbines				and other sources of income. Best of all,
generate electricity for homes and businesses				wind powers the economy without causing
and for sale to utilities.				pollution, generating hazardous wastes, or
				depleting natural resources.
There are two basic designs of wind electric
turbines: vertical-axis, or "egg-beater"				What are America's current sources of
style, and horizontal-axis machines.				electricity?
Horizontal-axis wind turbines are most
common, comprising more than 95% of the				Coal, the most polluting fuel and the largest
"utility-scale" (100 kilowatts (kW) capacity				source of the leading greenhouse gas, carbon
and larger) turbine market.				dioxide (CO2), is currently used to generate
				more than half of all of the electricity
Turbine subsystems include:				(52%) used in the United States. Other
				sources of electricity are: natural gas
a rotor, or blades, which convert the wind's				(15%), oil (4%), nuclear (19%), and
energy into rotational shaft energy;				hydropower (9%).

a nacelle containing a drive train, usually				How many people work in the U.S. wind
including a gearbox* and a generator;				industry?

a tower, to support the rotor and drive				The U.S. wind industry currently directly
train; and				employs more than 2,000 people. The wind
				industry contributes directly to the
electronic equipment such as controls,				economies of 46 states, with power plants and
electrical cables, ground support equipment,				manufacturing facilities that produce wind
and interconnection equipment.				turbines, blades, electronic components,
				gearboxes, generators, and a wide range of
Some turbines operate without a gearbox.				other equipment.

Wind turbines vary in size. This chart				The European Wind Energy Association (EWEA)
depicts a variety of turbine sizes and the				estimates that every megawatt of installed
amount of electricity they are each capable				wind capacity creates about 60 person-years
of generating (the turbine's capacity, or				of employment and 15-19 jobs, directly and
power rating).				indirectly. A typical 50-MW wind farm,
				therefore, creates some 3,000 person-years of
How much electricity can one wind turbine				employment. The rate of job creation will
generate?				decline as the industry grows and becomes
				able to make more use of efficiencies of
The ability to generate electricity is				volume, but wind and solar energy are still
measured in watts. Watts are very small				likely to furnish one of the largest sources
units, so the terms kilowatt (1,000 watts),				of new manufacturing jobs worldwide during
megawatt (1 million watts), and gigawatt (1				the 21st Century.
billion watts) are most commonly used to
describe the capacity of generating units				What is the value of export markets for wind?
like wind turbines or other power plants.
				Export markets are growing rapidly. Overseas
Electricity production and consumption are				markets account for about half of the
most commonly measured in kilowatt-hours				business of U.S. manufacturers of small wind
(kWh). A kilowatt-hour means 1,000 watts of				turbines and wind energy developers. Small
electricity produced or consumed for one				wind turbine markets are diverse and include
hour. One 50-watt light bulb left on for 20				many applications, both on-grid (connected to
hours consumes one kilowatt-hour of				a utility system) and off-grid (stand-alone).
electricity (50 watts x 20 hours = 1,000				A recent market study predicts that small
watt-hours = 1 kilowatt-hour).				wind turbine sales will increase fivefold by
				2005.
The output of a wind turbine depends on the
turbine's size and the wind's speed through				The potential economic benefits from wind are
the rotor. Wind turbines being manufactured				enormous. At a time when U.S. manufacturing
now have power ratings ranging from 250 watts				employment is generally on the decline, the
to 1.65 megawatts (MW).				production of wind equipment is one of the
				few potentially large sources of new
Example: A 10-kW wind turbine can generate				manufacturing jobs on the horizon.
about 16,000 kWh annually, more than enough
to power a typical household. A 1.65-MW				AWEA has estimated that wind installations
turbine can produce more than 4.7 million kWh				worldwide will total more than 48,000
in a year--enough to power more than 470				megawatts over the next decade, or more than
households. The average U.S. household				$45 billion worth of business. If the U.S.
consumes about 10,000 kWh of electricity each				industry could capture a 25% share of the
year.				global wind market through the year 2010,
				more than 150,000 new jobs would be created.
Example: A 250-kW turbine installed at the
elementary school in Spirit Lake, Iowa,				In what other ways does wind energy benefit
provides an average of 350,000 kWh of				the economy?
electricity per year, more than is necessary
for the 53,000-square-foot school. Excess				Wind farms can revitalize the economy of
electricity fed into the local utility system				rural communities, providing steady income
has earned the school $25,000 over five				through lease or royalty payments to farmers
years. The school uses electricity from the				and other landowners. Although leasing
utility at times when the wind does not blow.				arrangements can vary widely, a reasonable
				estimate for income to a landowner from a
Wind speed is a crucial element in projecting				single utility-scale turbine is about $2,000
turbine performance, and a site's wind speed				a year. For a 250-acre farm, with income from
is measured through wind resource assessment				wind at about $55 an acre, the annual income
prior to a wind system's construction.				from a wind lease would be $14,000, with no
Generally, annual average wind speeds greater				more than 2-3 acres removed from production.
than four meters per second (m/s) (9 mph) are				Farmers can grow crops or raise cattle next
required for small wind electric turbines				to the towers. Wind farms may extend over a
(less wind is required for water-pumping				large geographical area, but their actual
operations). Utility-scale wind power plants				"footprint" covers only a very small portion
require minimum average wind speeds of 6 m/s				of the land, making wind development an ideal
(13 mph).				way for farmers to earn additional income. In
				west Texas, for example, farmers are
The power available in the wind is				welcoming wind, as lease payments from this
proportional to the cube of its speed, which				new clean energy source replace declining
means that doubling the wind speed increases				payments from oil wells that have been
the available power by a factor of eight.				depleted.
Thus, a turbine operating at a site with an
average wind speed of 12 mph will generate				Farmers are not the only ones in rural
about 29% more electricity than one at an				communities to find that wind power can bring
11-mph site.				in income. In Spirit Lake, Iowa, the local
				school is earning savings and income from the
How many turbines does it take to make one				electricity generated by a turbine. In the
megawatt (MW)?				district of Forest City, Iowa, a turbine
				recently erected as a school project is
Most manufacturers of utility-scale turbines				expected to save $1.6 million in electricity
offer machines in the 700-kW to 1.65-MW				costs over its lifetime.
range. Ten 700-kW units would make a 7-MW
wind plant, while 10 1.65-MW machines would				Additional income is generated from one-time
make a 16.5-MW facility. In the future,				payments to construction contractors during
machines of larger size will be available.				installation, and from payments to turbine
				maintenance personnel on a long-term basis.
What is a wind power plant?				Wind farms also expand the local tax base,
				and keep energy dollars in the local
Wind plants can range in size from a few				community instead of spending them to pay for
megawatts to hundreds of megawatts in				coal or gas produced elsewhere. Alameda
capacity. Wind power plants are "modular,"				(Calif.) County, for example, collected
which means they consist of small individual				$725,000 in property taxes during 1998 from
modules (the turbines) and can easily be made				wind turbine installations valued at $66
larger or smaller as needed. Turbines can be				million.
added as electricity demand grows. Today, a
50-MW wind farm can be completed in 18 months				Wind energy and the environment
(including resource assessment).
				What are the environmental benefits of wind
What is "capacity factor"?				power?

A conventional utility power plant uses fuel,				Wind energy system operations do not generate
so it will normally run much of the time				air or water emissions and do not produce
unless it is idled by equipment problems or				hazardous waste. Nor do they deplete natural
for maintenance. A capacity factor of 40% to				resources such as coal, oil, or gas, or cause
80% is typical for conventional plants.				environmental damage through resource
				extraction and transportation. Wind's
A wind plant is "fueled" by the wind, which				pollution-free electricity can help reduce
blows steadily at times and not at all at				the environmental damage caused by power
other times. Most modern utility-scale wind				generation in the U.S. and worldwide.
turbines operate with a capacity factor of
25% to 40%, although they may achieve higher				In 1997, U.S. power plants emitted 70% of the
capacity factors during windy weeks or				sulfur dioxide, 34% of carbon dioxide, 33% of
months. It is possible to achieve much higher				nitrogen oxides, 28% of particulate matter
capacity factors by combining wind with a				and 23% of toxic heavy metals released into
storage technology such as pumped hydro or				our nation's environment, mostly the air.
compressed-air energy storage (CAES).				These figures are currently increasing in
				spite of efforts to roll back air pollution
What is "availability factor"?				through the federal Clean Air Act.

Availability factor (or just "availability)				Sulfur dioxide and nitrogen oxides cause acid
is a measurement of the reliability of a wind				rain. Acid rain harms forests and the
turbine or other power plant. It refers to				wildlife they support. Many lakes in the U.S.
the percentage of time that a plant is ready				Northeast have become biologically dead
to generate (that is, not out of service for				because of this form of pollution. Acid rain
maintenance or repairs). Modern wind turbines				also corrodes buildings and economic
have an availability of more than 98%--higher				infrastructure such as bridges.
than most other types of power plant. After
two decades of constant engineering				Carbon dioxide (CO2) is a greenhouse gas--its
refinement, today's wind machines are highly				buildup in the atmosphere contributes to
reliable.				global warming by trapping the sun's rays on
				the earth as in a greenhouse. The U.S., with
Wind energy costs				5% of the world's population, emits 23% of
				the world's CO2. The build-up of greenhouse
How much does wind energy cost?				gases is not only causing a gradual rise in
				average temperatures, but also seems to be
The National Renewable Energy Laboratory				increasing fluctuations in weather patterns
(NREL) is working with the wind industry to				and causing more severe droughts.
develop a next generation of wind turbine
technology. The products from this program				Particulate matter is of growing concern
are expected to generate electricity at				because of its impacts on health. Its
prices competitive with natural gas turbines,				presence in the air along with other
the least expensive conventional power				pollutants has contributed to make asthma one
source.				of the fastest growing childhood ailments in
				industrial and developing countries alike.
How do utility-scale wind power plants				Toxic heavy metals accumulate in the
compare in cost to other renewable energy				environment and up the biological food chain.
sources?
				Development of 10% of the wind potential in
Wind is the low-cost emerging renewable				the 10 windiest U.S. states would provide
energy resource.				more than enough energy to displace emissions
				from the nation's coal-fired power plants and
What is the "production tax credit" for wind				eliminate the nation's major source of acid
energy?				rain; reduce total U.S. emissions of CO2 by
				almost a third and world emissions of CO2 by
Generally, the credit is a business credit				4 %; and help contain the spread of asthma
that applies to electricity generated from				and other respiratory diseases aggravated or
wind plants for sale at wholesale (i.e., to a				caused by air pollution in this country.
utility or other electricity supplier). It
applies to electricity produced during the				If wind energy were to provide 20% of the
first 10 years of a wind plant's operation.				nation's electricity--a very realistic and
				achievable goal with the current
The wind PTC expired June 30, 1999, and an				technology--it could displace more than a
effort is currently underway to extend it for				third of the emissions from coal-fired power
five years. For information on the status of				plants, or all of radioactive waste and water
that effort, contact the American Wind Energy				pollution from nuclear power plants.
Association (AWEA), phone (202) 383-2500,
e-mail .				The 6 billion kilowatt-hours currently
				generated by wind plants in the U.S. each
Wind energy's potential				year displaced some 9 billion pounds (4.5
				million tons) of carbon dioxide, 23,500 tons
The wind doesn't blow all the time. How much				of sulfur dioxide (64 tons per day), and
can it really contribute to a utility's				15,500 tons of nitrogen oxides (42 tons per
generating capacity?				day).

However, in two separate studies, researchers				What are wind power's other environmental
have found that despite its intermittent				impacts?
nature, wind can provide capacity value for
utilities.				Wind power plants, like all other energy
				technologies, have some environmental
The studies, by the Tellus Institute of				impacts. However, unlike most conventional
Boston, Mass., and the Prince Edward Island				technologies (which have regional and even
(Canada) Energy Corp., concluded that when				global impacts due to their emissions), the
wind turbines are added to a utility system,				impacts of wind energy systems are local.
they increase the overall statistical				This makes them easier for local communities
probability that the system will be able to				to monitor and, if necessary, mitigate.
meet demand requirements. They noted that
while wind is an intermittent resource,				The local environmental impacts that can
conventional generating systems also				result from wind power development include:
experience periodic outages for maintenance
and repair.				Erosion, which can be prevented through
				proper installation and landscaping
The exact amount of capacity value that a				techniques. Erosion can be a concern in
given wind project provides depends on a				certain habitats such as the desert, where a
number of factors, including average wind				hard-packed soil surface must be disturbed to
speeds at the site and the match between wind				install wind turbines.
patterns and utility load requirements.
				Bird kills and other effects. Birds
How much energy can wind realistically supply				occasionally collide with wind turbines, as
to the U.S.?				they do with other tall structures such as
				buildings. Avian deaths have become a concern
Wind energy could supply about 20% of the				at Altamont Pass in California, which is an
nation's electricity, or 600 billion				area of extensive wind development and also
kilowatt-hours annually, according to				high year-round raptor use. Detailed studies
Battelle Pacific Northwest Laboratory, a				at other wind development areas indicate that
federal research lab. Wind energy resources				this is a site-specific issue that will not
useful for generating electricity can be				be a problem at most potential wind sites.
found in nearly every state.				However, areas that are commonly used by
				threatened or endangered species should be
U.S. wind resources are even greater,				regarded as unsuitable for wind development.
however. North Dakota alone is theoretically				The wind industry is working with
capable (if there were enough transmission				environmental groups, federal regulators, and
capacity, storage capability, etc.) of				other interested parties to develop methods
producing enough wind-generated power to meet				of measuring and mitigating wind energy's
more than one-third of U.S. electricity				effect on birds.
demand. The theoretical potentials of the
windiest states are shown in the following				Visual impacts, which can be minimized
table.				through careful design of a wind power plant.
				Using turbines of the same size and type and
Experience also shows that wind power can				spacing them uniformly generally results in a
provide at least up to a fifth of a system's				wind plant that satisfies most aesthetic
electricity, and the figure could probably be				concerns. Computer simulation is helpful in
higher. Wind power currently provides more				evaluating visual impacts before construction
than 20% of the electricity distributed by				begins. Public opinion polls show that the
Energia Hidroelectrica de Navarra, the				vast majority of people favor wind energy,
regional electric utility of the industrial				and support for wind plants often increases
state of Navarra in northern Spain. In				after they are actually installed and
western Denmark, wind supplies more than 25%				operating.
of the electricity that is used during windy
winter nights.				Noise was an issue with some early wind
				turbine designs, but it has been largely
How much energy can wind supply worldwide?				eliminated as a problem through improved
				engineering and through appropriate use of
According to the U.S. Department of Energy,				setbacks from nearby residences. Aerodynamic
the world's winds could theoretically supply				noise has been reduced by adjusting the
the equivalent of 5,800 quadrillion BTUs				thickness of the blades' trailing edges and
(quads) of energy each year--more than 15				by orienting blades upwind of the turbine
times current world energy demand. (A quad is				tower. A small amount of noise is generated
equal to about 172 million barrels of oil or				by the mechanical components of the turbine.
45 million tons of coal.)				To put this into perspective, a wind turbine
				250 meters from a residence is no noisier
A recent study performed by Denmark's BTM				than a kitchen refrigerator.
Consult for the European Wind Energy
Association and Greenpeace found that by the				How much land is needed for a utility-scale
year 2017, wind could provide 10% of world				wind plant?
electricity supplies, meeting the needs of
500 million average European households.				In open, flat terrain, a utility-scale wind
				plant will require about 50 acres per
The potential of wind to improve the quality				megawatt of installed capacity. However, only
of life in the world's developing countries,				5% (2.5 acres) or less of this area is
where more than two billion people live with				actually occupied by turbines, access roads,
no electricity or prospect of utility service				and other equipment--95% remains free for
in the foreseeable future, is vast.				other compatible uses such as farming or
				ranching. In California, Minnesota, Texas,
What is the "energy payback time" for a wind				and elsewhere, wind energy provides rural
turbine?				landowners and farmers with a supplementary
				source of income through leasing and royalty
The "energy payback time" is a term used to				arrangements with wind power developers.
measure the net energy value of a wind
turbine or other power plant--i.e., how long				A wind plant located on a ridgeline in hilly
does the plant have to operate to generate				terrain will require much less space, as
the amount of electricity that was required				little as two acres per megawatt.
for its manufacture and construction? Several
studies have looked at this question over the				How much water do wind turbines use compared
years and have concluded that wind energy has				with conventional power plants?
one of the shortest energy payback times of
any energy technology. A wind turbine				Water use can be a significant issue in
typically takes only a few months (3-8,				energy production, particularly in areas
depending on the average wind speed at its				where water is scarce, as conventional power
site) to "pay back" the energy needed for its				plants use large amounts of water for the
fabrication, installation, operation and				condensing portion of the thermodynamic
retirement.				cycle. For coal plants, water is also used to
				clean and process fuel.

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The advantages of using alternative energies

Everything about wind power