Wind power is the use of air flow through wind turbines to
mechanically power generators for electric power.
Wind power, as an
alternative to burning fossil fuels, is plentiful, renewable, widely
distributed, clean, produces no greenhouse gas emissions during
operation, consumes no water, and uses little land. The net effects
on the environment are far less problematic than those of nonrenewable
Wind farms consist of many individual wind turbines, which are
connected to the electric power transmission network. Onshore wind is
an inexpensive source of electric power, competitive with or in many
places cheaper than coal or gas plants. Offshore wind is
steadier and stronger than on land, and offshore farms have less
visual impact, but construction and maintenance costs are considerably
higher. Small onshore wind farms can feed some energy into the grid or
provide electric power to isolated off-grid locations.
Wind power gives variable power, which is very consistent from year to
year but has significant variation over shorter time scales. It is
therefore used in conjunction with other electric power sources to
give a reliable supply. As the proportion of wind power in a region
increases, a need to upgrade the grid, and a lowered ability to
supplant conventional production can occur. Power-management
techniques such as having excess capacity, geographically distributed
turbines, dispatchable backing sources, sufficient hydroelectric
power, exporting and importing power to neighboring areas, or reducing
demand when wind production is low, can in many cases overcome these
problems. In addition, weather forecasting permits the
electric-power network to be readied for the predictable variations in
production that occur.
As of 2015,
Denmark generates 40% of its electric power from
wind, and at least 83 other countries around the world are
using wind power to supply their electric power grids. In 2014,
global wind power capacity expanded 16% to 369,553 MW. Yearly wind
energy production is also growing rapidly and has reached around 4% of
worldwide electric power usage, 11.4% in the EU.
2.1 Generator characteristics and stability
2.2 Offshore wind power
2.3 Collection and transmission network
Wind power capacity and production
3.1 Growth trends
3.2 Capacity factor
3.7 Capacity credit, fuel savings and energy payback
Electric power cost and trends
4.2 Incentives and community benefits
5 Small-scale wind power
6 Environmental effects
7.1 Central government
7.2 Public opinion
8 Turbine design
11 See also
14 External links
Main article: History of wind power
Charles Brush's windmill of 1888, used for generating electric power.
Wind power has been used as long as humans have put sails into the
wind. For more than two millennia wind-powered machines have ground
grain and pumped water.
Wind power was widely available and not
confined to the banks of fast-flowing streams, or later, requiring
sources of fuel. Wind-powered pumps drained the polders of the
Netherlands, and in arid regions such as the
American mid-west or the
Australian outback, wind pumps provided water for live stock and steam
The first windmill used for the production of electric power was built
Scotland in July 1887 by
Prof James Blyth
Prof James Blyth of Anderson's College,
Glasgow (the precursor of Strathclyde University). Blyth's 10
metres (33 ft) high, cloth-sailed wind turbine was installed in
the garden of his holiday cottage at
was used to charge accumulators developed by the Frenchman Camille
Alphonse Faure, to power the lighting in the cottage, thus making
it the first house in the world to have its electric power supplied by
wind power. Blyth offered the surplus electric power to the people
Marykirk for lighting the main street, however, they turned down
the offer as they thought electric power was "the work of the
devil." Although he later built a wind turbine to supply emergency
power to the local Lunatic Asylum, Infirmary and Dispensary of
Montrose the invention never really caught on as the technology was
not considered to be economically viable.
Across the Atlantic, in
Cleveland, Ohio a larger and heavily
engineered machine was designed and constructed in the winter of
1887–1888 by Charles F. Brush, this was built by his engineering
company at his home and operated from 1886 until 1900. The Brush
wind turbine had a rotor 17 metres (56 ft) in diameter and was
mounted on an 18 metres (59 ft) tower. Although large by today's
standards, the machine was only rated at 12 kW. The connected
dynamo was used either to charge a bank of batteries or to operate up
to 100 incandescent light bulbs, three arc lamps, and various motors
in Brush's laboratory.
With the development of electric power, wind power found new
applications in lighting buildings remote from centrally-generated
power. Throughout the 20th century parallel paths developed small wind
stations suitable for farms or residences, and larger utility-scale
wind generators that could be connected to electric power grids for
remote use of power. Today wind powered generators operate in every
size range between tiny stations for battery charging at isolated
residences, up to near-gigawatt sized offshore wind farms that provide
electric power to national electrical networks.
Wind farm and List of onshore wind farms
Large onshore wind farms
Muppandal wind farm
Alta (Oak Creek-Mojave)
A wind farm is a group of wind turbines in the same location used for
production of electric power. A large wind farm may consist of several
hundred individual wind turbines distributed over an extended area,
but the land between the turbines may be used for agricultural or
other purposes. For example, Gansu
Wind Farm, the largest wind farm in
the world, has several thousand turbines. A wind farm may also be
Almost all large wind turbines have the same design — a
horizontal axis wind turbine having an upwind rotor with three blades,
attached to a nacelle on top of a tall tubular tower.
In a wind farm, individual turbines are interconnected with a medium
voltage (often 34.5 kV), power collection system and communications
network. In general, a distance of 7D (7 × Rotor Diameter of the Wind
Turbine) is set between each turbine in a fully developed wind
farm. At a substation, this medium-voltage electric current is
increased in voltage with a transformer for connection to the high
voltage electric power transmission system.
Generator characteristics and stability
Induction generators, which were often used for wind power projects in
the 1980s and 1990s, require reactive power for excitation so
substations used in wind-power collection systems include substantial
capacitor banks for power factor correction. Different types of wind
turbine generators behave differently during transmission grid
disturbances, so extensive modelling of the dynamic electromechanical
characteristics of a new wind farm is required by transmission system
operators to ensure predictable stable behaviour during system faults.
In particular, induction generators cannot support the system voltage
during faults, unlike steam or hydro turbine-driven synchronous
Today these generators aren't used any more in modern turbines.
Instead today most turbines use variable speed generators combined
with partial- or full-scale power converter between the turbine
generator and the collector system, which generally have more
desirable properties for grid interconnection and have Low voltage
ride through-capabilities. Modern concepts use either doubly fed
machines with partial-scale converters or squirrel-cage induction
generators or synchronous generators (both permanently and
electrically excited) with full scale converters.
Transmission systems operators will supply a wind farm developer with
a grid code to specify the requirements for interconnection to the
transmission grid. This will include power factor, constancy of
frequency and dynamic behaviour of the wind farm turbines during a
Offshore wind power
The world's second full-scale floating wind turbine (and first to be
installed without the use of heavy-lift vessels), WindFloat, operating
at rated capacity (2 MW) approximately 5 km offshore of
Póvoa de Varzim, Portugal
Offshore wind power
Offshore wind power and List of offshore wind farms
Offshore wind power
Offshore wind power refers to the construction of wind farms in large
bodies of water to generate electric power. These installations can
utilize the more frequent and powerful winds that are available in
these locations and have less aesthetic impact on the landscape than
land based projects. However, the construction and the maintenance
costs are considerably higher.
Vestas are the leading turbine suppliers for offshore wind
power. DONG Energy,
E.ON are the leading offshore
operators. As of October 2010, 3.16 GW of offshore wind power
capacity was operational, mainly in Northern Europe. According to BTM
Consult, more than 16 GW of additional capacity will be installed
before the end of 2014 and the UK and
Germany will become the two
Offshore wind power
Offshore wind power capacity is expected to reach a
total of 75 GW worldwide by 2020, with significant contributions from
China and the US. The UK's investments in offshore wind power have
resulted in a rapid decrease of the usage of coal as an energy source
between 2012 and 2017, as well as a drop in the usage of natural gas
as an energy source in 2017.
In 2012, 1,662 turbines at 55 offshore wind farms in 10 European
countries produced 18 TWh, enough to power almost five million
households. As of August 2013 the
London Array in the United
Kingdom is the largest offshore wind farm in the world at 630 MW. This
is followed by
Gwynt y Môr
Gwynt y Môr (576 MW), also in the UK.
World's largest offshore wind farms
Turbines and model
Gwynt y Môr
Siemens SWT-3.6 107
BARD Offshore 1
80 BARD 5.0 turbines
Collection and transmission network
In a wind farm, individual turbines are interconnected with a medium
voltage (usually 34.5 kV) power collection system and communications
network. At a substation, this medium-voltage electric current is
increased in voltage with a transformer for connection to the high
voltage electric power transmission system.
Wind Power in Serbia
A transmission line is required to bring the generated power to (often
remote) markets. For an off-shore station this may require a submarine
cable. Construction of a new high-voltage line may be too costly for
the wind resource alone, but wind sites may take advantage of lines
installed for conventionally fueled generation.
One of the biggest current challenges to wind power grid integration
in the United States is the necessity of developing new transmission
lines to carry power from wind farms, usually in remote lowly
populated states in the middle of the country due to availability of
wind, to high load locations, usually on the coasts where population
density is higher. The current transmission lines in remote locations
were not designed for the transport of large amounts of energy. As
transmission lines become longer the losses associated with power
transmission increase, as modes of losses at lower lengths are
exacerbated and new modes of losses are no longer negligible as the
length is increased, making it harder to transport large loads over
large distances. However, resistance from state and local
governments makes it difficult to construct new transmission lines.
Multi state power transmission projects are discouraged by states with
cheap electric power rates for fear that exporting their cheap power
will lead to increased rates. A 2005 energy law gave the Energy
Department authority to approve transmission projects states refused
to act on, but after an attempt to use this authority, the Senate
declared the department was being overly aggressive in doing so.
Another problem is that wind companies find out after the fact that
the transmission capacity of a new farm is below the generation
capacity, largely because federal utility rules to encourage renewable
energy installation allow feeder lines to meet only minimum standards.
These are important issues that need to be solved, as when the
transmission capacity does not meet the generation capacity, wind
farms are forced to produce below their full potential or stop running
all together, in a process known as curtailment. While this leads to
potential renewable generation left untapped, it prevents possible
grid overload or risk to reliable service.
Wind power capacity and production
Wind power by country
Worldwide wind generation up to 2012
Global annual new installed wind capacity 1997–2015 (in MW):3
As of 2015, there are over 200,000 wind turbines operating, with a
total nameplate capacity of 432 GW worldwide. The European Union
passed 100 GW nameplate capacity in September 2012, while the
United States surpassed 75 GW in 2015 and China's grid connected
capacity passed 145 GW in 2015. In 2015 wind power constituted
15.6% of all installed power generation capacity in the European Union
and it generated around 11.4% of its power.
World wind generation capacity more than quadrupled between 2000 and
2006, doubling about every 3 years. The United States pioneered wind
farms and led the world in installed capacity in the 1980s and into
the 1990s. In 1997 installed capacity in
Germany surpassed the United
States and led until once again overtaken by the United States in
2008. China has been rapidly expanding its wind installations in the
late 2000s and passed the United States in 2010 to become the world
leader. As of 2011, 83 countries around the world were using wind
power on a commercial basis.
The actual amount of electric power that wind is able to generate is
calculated by multiplying the nameplate capacity by the capacity
factor, which varies according to equipment and location. Estimates of
the capacity factors for wind installations are in the range of 35% to
China: 23,351 MW (45.4%)
Germany: 5,279 MW (10.3%)
United States: 4,854 MW (9.4%)
Brazil: 2,472 MW (4.8%)
India: 2,315 MW (4.5%)
Canada: 1,871 MW (3.6%)
United Kingdom: 1,736 MW (3.4%)
Sweden: 1,050 MW (2.0%)
France: 1,042 MW (2.0%)
Turkey: 804 MW (1.6%)
Rest of the world: 6,702 MW (13.0%)
Worldwide new installed capacity, 2014
China: 114,763 MW (31.1%)
United States: 65,879 MW (17.8%)
Germany: 39,165 MW (10.6%)
Spain: 22,987 MW (6.2%)
India: 22,465 MW (6.1%)
United Kingdom: 12,440 MW (3.4%)
Canada: 9,694 MW (2.6%)
France: 9,285 MW (2.5%)
Italy: 8,663 MW (2.3%)
Brazil: 5,939 MW (1.6%)
Rest of the world: 58,275 MW (15.8%)
Worldwide cumulative capacity, 2014
Top wind power producing countries in 2015
(rest of world)
Worldwide installed wind power capacity forecast
The wind power industry set new records in 2014 – more than 50 GW of
new capacity was installed. Another record breaking year occurred in
2015, with 22% annual market growth resulting in the 60 GW mark being
passed. In 2015, close to half of all new wind power was added
outside of the traditional markets in
Europe and North America. This
was largely from new construction in China and India. Global Wind
Energy Council (GWEC) figures show that 2015 recorded an increase of
installed capacity of more than 63 GW, taking the total installed wind
energy capacity to 432.9 GW, up from 74 GW in 2006. In terms of
economic value, the wind energy sector has become one of the important
players in the energy markets, with the total investments reaching
US$329bn (€296.6bn), an increase of 4% over 2014.
Although the wind power industry was affected by the global financial
crisis in 2009 and 2010, GWEC predicts that the installed capacity of
wind power will be 792.1 GW by the end of 2020 and 4,042 GW by end
of 2050. The increased commissioning of wind power is being
accompanied by record low prices for forthcoming renewable electric
power. In some cases, wind onshore is already the cheapest electric
power generation option and costs are continuing to decline. The
contracted prices for wind onshore for the next few years are now as
low as 30 USD/MWh.
In the EU in 2015, 44% of all new generating capacity was wind power;
while in the same period net fossil fuel power capacity decreased.
Since wind speed is not constant, a wind farm's annual energy
production is never as much as the sum of the generator nameplate
ratings multiplied by the total hours in a year. The ratio of actual
productivity in a year to this theoretical maximum is called the
capacity factor. Typical capacity factors are 15–50%; values at the
upper end of the range are achieved in favourable sites and are due to
wind turbine design improvements.[nb 1]
Online data is available for some locations, and the capacity factor
can be calculated from the yearly output. For example, the
German nationwide average wind power capacity factor over all of 2012
was just under 17.5% (45,867 GW·h/yr / (29.9 GW × 24 × 366) =
0.1746), and the capacity factor for Scottish wind farms averaged
24% between 2008 and 2010.
Unlike fueled generating plants, the capacity factor is affected by
several parameters, including the variability of the wind at the site
and the size of the generator relative to the turbine's swept area. A
small generator would be cheaper and achieve a higher capacity factor
but would produce less electric power (and thus less profit) in high
winds. Conversely, a large generator would cost more but generate
little extra power and, depending on the type, may stall out at low
wind speed. Thus an optimum capacity factor of around 40–50% would
be aimed for.
A 2008 study released by the U.S. Department of
Energy noted that the
capacity factor of new wind installations was increasing as the
technology improves, and projected further improvements for future
capacity factors. In 2010, the department estimated the capacity
factor of new wind turbines in 2010 to be 45%. The annual average
capacity factor for wind generation in the US has varied between 29.8%
and 34% during the period 2010–2015.
United Kingdom (2015)
United States (2016)
Wind energy penetration is the fraction of energy produced by wind
compared with the total generation. The wind power penetration in
world electric power generation in 2015 was 3.5%.
There is no generally accepted maximum level of wind penetration. The
limit for a particular grid will depend on the existing generating
plants, pricing mechanisms, capacity for energy storage, demand
management and other factors. An interconnected electric power grid
will already include reserve generating and transmission capacity to
allow for equipment failures. This reserve capacity can also serve to
compensate for the varying power generation produced by wind stations.
Studies have indicated that 20% of the total annual electrical energy
consumption may be incorporated with minimal difficulty. These
studies have been for locations with geographically dispersed wind
farms, some degree of dispatchable energy or hydropower with storage
capacity, demand management, and interconnected to a large grid area
enabling the export of electric power when needed. Beyond the 20%
level, there are few technical limits, but the economic implications
become more significant. Electrical utilities continue to study the
effects of large scale penetration of wind generation on system
stability and economics.
A wind energy penetration figure can be specified for different
duration of time, but is often quoted annually. To obtain 100% from
wind annually requires substantial long term storage or substantial
interconnection to other systems which may already have substantial
storage. On a monthly, weekly, daily, or hourly basis—or less—wind
might supply as much as or more than 100% of current use, with the
rest stored or exported. Seasonal industry might then take advantage
of high wind and low usage times such as at night when wind output can
exceed normal demand. Such industry might include production of
silicon, aluminum, steel, or of natural gas, and hydrogen, and
using future long term storage to facilitate 100% energy from variable
renewable energy. Homes can also be programmed to accept extra
electric power on demand, for example by remotely turning up water
In Australia, the state of South Australia generates around half of
the nation's wind power capacity. By the end of 2011 wind power in
South Australia, championed by Premier (and Climate Change Minister)
Mike Rann, reached 26% of the State's electric power generation,
edging out coal for the first time. At this stage South Australia,
with only 7.2% of Australia's population, had 54% of Australia's
Main article: Variable renewable energy
Further information: Grid balancing
Wind turbines are typically installed in favorable windy locations. In
the image, wind power generators in Spain, near an Osborne bull.
Electric power generated from wind power can be highly variable at
several different timescales: hourly, daily, or seasonally. Annual
variation also exists, but is not as significant. Because
instantaneous electrical generation and consumption must remain in
balance to maintain grid stability, this variability can present
substantial challenges to incorporating large amounts of wind power
into a grid system. Intermittency and the non-dispatchable nature of
wind energy production can raise costs for regulation, incremental
operating reserve, and (at high penetration levels) could require an
increase in the already existing energy demand management, load
shedding, storage solutions or system interconnection with HVDC
cables. The variability of wind is quite different from solar, wind
may be producing power at night when other baseload plants are often
Fluctuations in load and allowance for failure of large fossil-fuel
generating units requires operating reserve capacity, which can be
increased to compensate for variability of wind generation.
Wind power is variable, and during low wind periods it must be
replaced by other power sources. Transmission networks presently cope
with outages of other generation plants and daily changes in
electrical demand, but the variability of intermittent power sources
such as wind power, is more frequent than those of conventional power
generation plants which, when scheduled to be operating, may be able
to deliver their nameplate capacity around 95% of the time.
Presently, grid systems with large wind penetration require a small
increase in the frequency of usage of natural gas spinning reserve
power plants to prevent a loss of electric power in the event that
there is no wind. At low wind power penetration, this is less of an
GE has installed a prototype wind turbine with onboard battery similar
to that of an electric car, equivalent of 1 minute of production.
Despite the small capacity, it is enough to guarantee that power
output complies with forecast for 15 minutes, as the battery is used
to eliminate the difference rather than provide full output. In
certain cases the increased predictability can be used to take wind
power penetration from 20 to 30 or 40 per cent. The battery cost can
be retrieved by selling burst power on demand and reducing backup
needs from gas plants.
In the UK there were 124 separate occasions from 2008 to 2010 when the
nation's wind output fell to less than 2% of installed capacity.
A report on Denmark's wind power noted that their wind power network
provided less than 1% of average demand on 54 days during the year
Wind power advocates argue that these periods of low wind
can be dealt with by simply restarting existing power stations that
have been held in readiness, or interlinking with HVDC.
Electrical grids with slow-responding thermal power plants and without
ties to networks with hydroelectric generation may have to limit the
use of wind power. According to a 2007 Stanford University study
published in the Journal of Applied Meteorology and Climatology,
interconnecting ten or more wind farms can allow an average of 33% of
the total energy produced (i.e. about 8% of total nameplate capacity)
to be used as reliable, baseload electric power which can be relied on
to handle peak loads, as long as minimum criteria are met for wind
speed and turbine height.
Conversely, on particularly windy days, even with penetration levels
of 16%, wind power generation can surpass all other electric power
sources in a country. In Spain, in the early hours of 16 April 2012
wind power production reached the highest percentage of electric power
production till then, at 60.46% of the total demand. In Denmark,
which had power market penetration of 30% in 2013, over 90 hours,
wind power generated 100% of the country's power, peaking at 122% of
the country's demand at 2 am on 28 October.
Increase in system operation costs, Euros per MWh, for 10% & 20%
A 2006 International
Energy Agency forum presented costs for managing
intermittency as a function of wind-energy's share of total capacity
for several countries, as shown in the table on the right. Three
reports on the wind variability in the UK issued in 2009, generally
agree that variability of wind needs to be taken into account by
adding 20% to the operating reserve, but it does not make the grid
unmanageable. The additional costs, which are modest, can be
The combination of diversifying variable renewables by type and
location, forecasting their variation, and integrating them with
dispatchable renewables, flexible fueled generators, and demand
response can create a power system that has the potential to meet
power supply needs reliably. Integrating ever-higher levels of
renewables is being successfully demonstrated in the real world:
In 2009, eight American and three European authorities, writing in the
leading electrical engineers' professional journal, didn't find "a
credible and firm technical limit to the amount of wind energy that
can be accommodated by electric power grids". In fact, not one of more
than 200 international studies, nor official studies for the eastern
and western U.S. regions, nor the International
Energy Agency, has
found major costs or technical barriers to reliably integrating up to
30% variable renewable supplies into the grid, and in some studies
Solar power tends to be complementary to wind. On daily to
weekly timescales, high pressure areas tend to bring clear skies and
low surface winds, whereas low pressure areas tend to be windier and
cloudier. On seasonal timescales, solar energy peaks in summer,
whereas in many areas wind energy is lower in summer and higher in
winter.[nb 2] Thus the seasonal variation of wind and solar power
tend to cancel each other somewhat. In 2007 the Institute for Solar
Energy Supply Technology of the
University of Kassel
University of Kassel pilot-tested a
combined power plant linking solar, wind, biogas and hydrostorage to
provide load-following power around the clock and throughout the year,
entirely from renewable sources.
Wind power forecasting
Wind power forecasting methods are used, but predictability of any
particular wind farm is low for short-term operation. For any
particular generator there is an 80% chance that wind output will
change less than 10% in an hour and a 40% chance that it will change
10% or more in 5 hours.
However, studies by Graham Sinden (2009) suggest that, in practice,
the variations in thousands of wind turbines, spread out over several
different sites and wind regimes, are smoothed. As the distance
between sites increases, the correlation between wind speeds measured
at those sites, decreases.
Thus, while the output from a single turbine can vary greatly and
rapidly as local wind speeds vary, as more turbines are connected over
larger and larger areas the average power output becomes less variable
and more predictable.
Wind power hardly ever suffers major technical failures, since
failures of individual wind turbines have hardly any effect on overall
power, so that the distributed wind power is reliable and
predictable,[unreliable source?] whereas conventional generators,
while far less variable, can suffer major unpredictable outages.
Main article: Grid energy storage
See also: List of energy storage projects
The Sir Adam Beck Generating Complex at Niagara Falls, Canada,
includes a large pumped-storage hydroelectricity reservoir. During
hours of low electrical demand excess electrical grid power is used to
pump water up into the reservoir, which then provides an extra 174 MW
of electric power during periods of peak demand.
Typically, conventional hydroelectricity complements wind power very
well. When the wind is blowing strongly, nearby hydroelectric stations
can temporarily hold back their water. When the wind drops they can,
provided they have the generation capacity, rapidly increase
production to compensate. This gives a very even overall power supply
and virtually no loss of energy and uses no more water.
Alternatively, where a suitable head of water is not available,
pumped-storage hydroelectricity or other forms of grid energy storage
such as compressed air energy storage and thermal energy storage can
store energy developed by high-wind periods and release it when
needed. The type of storage needed depends on the wind penetration
level – low penetration requires daily storage, and high penetration
requires both short and long term storage – as long as a month or
more. Stored energy increases the economic value of wind energy since
it can be shifted to displace higher cost generation during peak
demand periods. The potential revenue from this arbitrage can offset
the cost and losses of storage. For example, in the UK, the 1.7 GW
Dinorwig pumped-storage plant evens out electrical demand peaks, and
allows base-load suppliers to run their plants more efficiently.
Although pumped-storage power systems are only about 75% efficient,
and have high installation costs, their low running costs and ability
to reduce the required electrical base-load can save both fuel and
total electrical generation costs.
In particular geographic regions, peak wind speeds may not coincide
with peak demand for electrical power. In the U.S. states of
California and Texas, for example, hot days in summer may have low
wind speed and high electrical demand due to the use of air
conditioning. Some utilities subsidize the purchase of geothermal heat
pumps by their customers, to reduce electric power demand during the
summer months by making air conditioning up to 70% more
efficient; widespread adoption of this technology would better
match electric power demand to wind availability in areas with hot
summers and low summer winds. A possible future option may be to
interconnect widely dispersed geographic areas with an HVDC "super
grid". In the U.S. it is estimated that to upgrade the transmission
system to take in planned or potential renewables would cost at least
USD 60 bn, while the society value of added windpower would be
more than that cost.
Germany has an installed capacity of wind and solar that can exceed
daily demand, and has been exporting peak power to neighboring
countries, with exports which amounted to some 14.7 billion kWh in
2012. A more practical solution is the installation of thirty
days storage capacity able to supply 80% of demand, which will become
necessary when most of Europe's energy is obtained from wind power and
solar power. Just as the EU requires member countries to maintain 90
days strategic reserves of oil it can be expected that countries will
provide electric power storage, instead of expecting to use their
neighbors for net metering.
Capacity credit, fuel savings and energy payback
The capacity credit of wind is estimated by determining the capacity
of conventional plants displaced by wind power, whilst maintaining the
same degree of system security. According to the American
Energy Association, production of wind power in the United States
in 2015 avoided consumption of 73 billion gallons of water and reduced
CO2 emissions by 132 million metric tons, while providing USD 7.3 bn
in public health savings.
The energy needed to build a wind farm divided into the total output
over its life,
Energy Return on
Energy Invested, of wind power varies
but averages about 20–25. Thus, the energy payback time is
typically around a year.
Wind turbines reached grid parity (the point at which the cost of wind
power matches traditional sources) in some areas of
Europe in the
mid-2000s, and in the US around the same time. Falling prices continue
to drive the levelized cost down and it has been suggested that it has
reached general grid parity in
Europe in 2010, and will reach the same
point in the US around 2016 due to an expected reduction in capital
costs of about 12%.
Electric power cost and trends
Estimated cost per MWh for wind power in Denmark
The National Renewable
Energy Laboratory projects that the levelized
cost of wind power in the U.S. will decline about 25% from 2012 to
A turbine blade convoy passing through
Edenfield in the U.K. (2008).
Even longer two-piece blades are now manufactured, and then assembled
on-site to reduce difficulties in transportation.
Wind power is capital intensive, but has no fuel costs. The price
of wind power is therefore much more stable than the volatile prices
of fossil fuel sources. The marginal cost of wind energy once a
station is constructed is usually less than 1-cent per kW·h.
However, the estimated average cost per unit of electric power must
incorporate the cost of construction of the turbine and transmission
facilities, borrowed funds, return to investors (including cost of
risk), estimated annual production, and other components, averaged
over the projected useful life of the equipment, which may be in
excess of twenty years.
Energy cost estimates are highly dependent on
these assumptions so published cost figures can differ substantially.
In 2004, wind energy cost a fifth of what it did in the 1980s, and
some expected that downward trend to continue as larger multi-megawatt
turbines were mass-produced. In 2012 capital costs for wind
turbines were substantially lower than 2008–2010 but still above
2002 levels. A 2011 report from the American
Association stated, "Wind's costs have dropped over the past two
years, in the range of 5 to 6 cents per kilowatt-hour recently....
about 2 cents cheaper than coal-fired electric power, and more
projects were financed through debt arrangements than tax equity
structures last year.... winning more mainstream acceptance from Wall
Street's banks.... Equipment makers can also deliver products in the
same year that they are ordered instead of waiting up to three years
as was the case in previous cycles.... 5,600 MW of new installed
capacity is under construction in the United States, more than double
the number at this point in 2010. Thirty-five percent of all new power
generation built in the United States since 2005 has come from wind,
more than new gas and coal plants combined, as power providers are
increasingly enticed to wind as a convenient hedge against
unpredictable commodity price moves."
Energy Association report gives an average generation
cost of onshore wind power of around 3.2 pence (between US 5 and 6
cents) per kW·h (2005). Cost per unit of energy produced was
estimated in 2006 to be 5 to 6 percent above the cost of new
generating capacity in the US for coal and natural gas: wind cost was
estimated at $55.80 per MW·h, coal at $53.10/MW·h and natural gas at
$52.50. Similar comparative results with natural gas were
obtained in a governmental study in the UK in 2011. In 2011 power
from wind turbines could be already cheaper than fossil or nuclear
plants; it is also expected that wind power will be the cheapest form
of energy generation in the future. The presence of wind energy,
even when subsidised, can reduce costs for consumers (€5 billion/yr
in Germany) by reducing the marginal price, by minimising the use of
expensive peaking power plants.
An 2012 EU study shows base cost of onshore wind power similar to
coal, when subsidies and externalities are disregarded.
Wind power has
some of the lowest external costs.
In February 2013 Bloomberg New
Energy Finance (BNEF) reported that the
cost of generating electric power from new wind farms is cheaper than
new coal or new baseload gas plants. When including the current
Australian federal government carbon pricing scheme their modeling
gives costs (in Australian dollars) of $80/MWh for new wind farms,
$143/MWh for new coal plants and $116/MWh for new baseload gas plants.
The modeling also shows that "even without a carbon price (the most
efficient way to reduce economy-wide emissions) wind energy is 14%
cheaper than new coal and 18% cheaper than new gas." Part of the
higher costs for new coal plants is due to high financial lending
costs because of "the reputational damage of emissions-intensive
investments". The expense of gas fired plants is partly due to "export
market" effects on local prices. Costs of production from coal fired
plants built in "the 1970s and 1980s" are cheaper than renewable
energy sources because of depreciation. In 2015 BNEF calculated
LCOE prices per MWh energy in new powerplants (excluding carbon
costs) : $85 for onshore wind ($175 for offshore), $66–75 for
coal in the Americas ($82–105 in Europe), gas
$80–100. A 2014 study showed unsubsidized
between $37–81, depending on region. A 2014 US DOE report
showed that in some cases power purchase agreement prices for wind
power had dropped to record lows of $23.5/MWh.
The cost has reduced as wind turbine technology has improved. There
are now longer and lighter wind turbine blades, improvements in
turbine performance and increased power generation efficiency. Also,
wind project capital and maintenance costs have continued to
decline. For example, the wind industry in the USA in early 2014
were able to produce more power at lower cost by using taller wind
turbines with longer blades, capturing the faster winds at higher
elevations. This has 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 can now compete with
conventional fossil fuels like coal. Prices have fallen to about 4
cents per kilowatt-hour in some cases and utilities have been
increasing the amount of wind energy in their portfolio, saying it is
their cheapest option.
A number of initiatives are working to reduce costs of electric power
from offshore wind. One example is the
Carbon Trust Offshore Wind
Accelerator, a joint industry project, involving nine offshore wind
developers, which aims to reduce the cost of offshore wind by 10% by
2015. It has been suggested that innovation at scale could deliver 25%
cost reduction in offshore wind by 2020. Henrik Stiesdal, former
Chief Technical Officer at
Wind Power, has stated that by 2025
energy from offshore wind will be one of the cheapest, scalable
solutions in the UK, compared to other renewables and fossil fuel
energy sources, if the true cost to society is factored into the cost
of energy equation. He calculates the cost at that time to be 43
EUR/MWh for onshore, and 72 EUR/MWh for offshore wind.
In August 2017, the Department of Energy's National Renewable Energy
Laboratory (NREL) published a new report on a 50% reduction in wind
power cost by 2030. The NREL is expected to achieve advances in wind
turbine design, materials and controls to unlock performance
improvements and reduce costs. According to international surveyors,
this study shows that cost cutting is projected to fluctuate between
24% and 30% by 2030. In more aggressive cases, experts estimate cost
reduction Up to 40 percent if the research and development and
technology programs result in additional efficiency.
Incentives and community benefits
U.S. landowners typically receive $3,000–$5,000 annual rental income
per wind turbine, while farmers continue to grow crops or graze cattle
up to the foot of the turbines. Shown: the Brazos
Some of the 6,000 turbines in California's Altamont Pass
aided by tax incentives during the 1980s.
The U.S. wind industry generates tens of thousands of jobs and
billions of dollars of economic activity.
Wind projects provide
local taxes, or payments in lieu of taxes and strengthen the economy
of rural communities by providing income to farmers with wind turbines
on their land.
Wind energy in many jurisdictions receives
financial or other support to encourage its development.
benefits from subsidies in many jurisdictions, either to increase its
attractiveness, or to compensate for subsidies received by other forms
of production which have significant negative externalities.
In the US, wind power receives a production tax credit (PTC) of
1.5¢/kWh in 1993 dollars for each kW·h produced, for the first ten
years; at 2.2 cents per kW·h in 2012, the credit was renewed on 2
January 2012, to include construction begun in 2013. A 30% tax
credit can be applied instead of receiving the PTC. Another
tax benefit is accelerated depreciation. Many American states also
provide incentives, such as exemption from property tax, mandated
purchases, and additional markets for "green credits". The Energy
Improvement and Extension Act of 2008 contains extensions of credits
for wind, including microturbines. Countries such as
Germany also provide incentives for wind turbine construction, such as
tax credits or minimum purchase prices for wind generation, with
assured grid access (sometimes referred to as feed-in tariffs). These
feed-in tariffs are typically set well above average electric power
prices. In December 2013 U.S. Senator
Lamar Alexander and
other Republican senators argued that the "wind energy production tax
credit should be allowed to expire at the end of 2013" and it
expired 1 January 2014 for new installations.
Secondary market forces also provide incentives for businesses to use
wind-generated power, even if there is a premium price for the
electricity. For example, socially responsible manufacturers pay
utility companies a premium that goes to subsidize and build new wind
power infrastructure. Companies use wind-generated power, and in
return they can claim that they are undertaking strong "green"
efforts. In the US the organization Green-e monitors business
compliance with these renewable energy credits. Turbine prices
have fallen significantly in recent years due to tougher competitive
conditions such as the increased use of energy auctions, and the
elimination of subsidies in many markets. For example, Vestas, a wind
turbine manufacturer, whose largest onshore turbine can pump out 4.2
megawatts of power, enough to provide electricity to roughly 5,000
homes, has seen prices for its turbines fall from €950,000 per
megawatt in late 2016, to around €800,000 per megawatt in the third
quarter of 2017.
Small-scale wind power
Further information: Microgeneration
A small Quietrevolution QR5 Gorlov type vertical axis wind turbine on
the roof of
Colston Hall in Bristol, England. Measuring 3 m in
diameter and 5 m high, it has a nameplate rating of 6.5 kW.
Small-scale wind power is the name given to wind generation systems
with the capacity to produce up to 50 kW of electrical
power. Isolated communities, that may otherwise rely on diesel
generators, may use wind turbines as an alternative. Individuals may
purchase these systems to reduce or eliminate their dependence on grid
electric power for economic reasons, or to reduce their carbon
Wind turbines have been used for household electric power
generation in conjunction with battery storage over many decades in
Recent examples of small-scale wind power projects in an urban setting
can be found in New York City, where, since 2009, a number of building
projects have capped their roofs with Gorlov-type helical wind
turbines. Although the energy they generate is small compared to the
buildings' overall consumption, they help to reinforce the building's
'green' credentials in ways that "showing people your high-tech
boiler" can not, with some of the projects also receiving the direct
support of the New York State
Energy Research and Development
Grid-connected domestic wind turbines may use grid energy storage,
thus replacing purchased electric power with locally produced power
when available. The surplus power produced by domestic microgenerators
can, in some jurisdictions, be fed into the network and sold to the
utility company, producing a retail credit for the microgenerators'
owners to offset their energy costs.
Off-grid system users can either adapt to intermittent power or use
batteries, photovoltaic or diesel systems to supplement the wind
turbine. Equipment such as parking meters, traffic warning signs,
street lighting, or wireless Internet gateways may be powered by a
small wind turbine, possibly combined with a photovoltaic system, that
charges a small battery replacing the need for a connection to the
Carbon Trust study into the potential of small-scale wind energy in
the UK, published in 2010, found that small wind turbines could
provide up to 1.5 terawatt hours (TW·h) per year of electric power
(0.4% of total UK electric power consumption), saving 0.6 million
tonnes of carbon dioxide (Mt CO2) emission savings. This is based on
the assumption that 10% of households would install turbines at costs
competitive with grid electric power, around 12 pence (US 19 cents) a
kW·h. A report prepared for the UK's government-sponsored Energy
Saving Trust in 2006, found that home power generators of various
kinds could provide 30 to 40% of the country's electric power needs by
Distributed generation from renewable resources is increasing as a
consequence of the increased awareness of climate change. The
electronic interfaces required to connect renewable generation units
with the utility system can include additional functions, such as the
active filtering to enhance the power quality.
Main article: Environmental impact of wind power
Livestock grazing near a wind turbine.
The environmental impact of wind power when compared to the
environmental impacts of fossil fuels, is relatively minor. According
to the IPCC, in assessments of the life-cycle global warming potential
of energy sources, wind turbines have a median value of between 12 and
11 (gCO2eq/kWh) depending on whether off- or onshore turbines are
being assessed. Compared with other low carbon power
sources, wind turbines have some of the lowest global warming
potential per unit of electrical energy generated.
While a wind farm may cover a large area of land, many land uses such
as agriculture are compatible with it, as only small areas of turbine
foundations and infrastructure are made unavailable for use.
There are reports of bird and bat mortality at wind turbines as there
are around other artificial structures. The scale of the ecological
impact may or may not be significant, depending on specific
circumstances. Prevention and mitigation of wildlife fatalities, and
protection of peat bogs, affect the siting and operation of wind
Wind turbines generate some noise. At a residential distance of 300
metres (980 ft) this may be around 45 dB, which is slightly
louder than a refrigerator. At 1.5 km (1 mi) distance they
become inaudible. There are anecdotal reports of negative
health effects from noise on people who live very close to wind
turbines. Peer-reviewed research has generally not supported
The United States Air Force and Navy have expressed concern that
siting large wind turbines near bases "will negatively impact radar to
the point that air traffic controllers will lose the location of
Aesthetic aspects of wind turbines and resulting changes of the visual
landscape are significant. Conflicts arise especially in scenic
and heritage protected landscapes.
Part of the Seto Hill Windfarm in Japan.
Nuclear power and fossil fuels are subsidized by many governments, and
wind power and other forms of renewable energy are also often
subsidized. For example, a 2009 study by the Environmental Law
Institute assessed the size and structure of U.S. energy
subsidies over the 2002–2008 period. The study estimated that
subsidies to fossil-fuel based sources amounted to approximately $72
billion over this period and subsidies to renewable fuel sources
totalled $29 billion. In the United States, the federal government has
paid US$74 billion for energy subsidies to support R&D for
nuclear power ($50 billion) and fossil fuels ($24 billion) from 1973
to 2003. During this same time frame, renewable energy technologies
and energy efficiency received a total of US$26 billion. It has
been suggested that a subsidy shift would help to level the playing
field and support growing energy sectors, namely solar power, wind
power, and biofuels. History shows that no energy sector was
developed without subsidies.
According to the International
Energy Agency (IEA) (2011), energy
subsidies artificially lower the price of energy paid by consumers,
raise the price received by producers or lower the cost of production.
Fossil fuels subsidies costs generally outweigh the benefits.
Subsidies to renewables and low-carbon energy technologies can bring
long-term economic and environmental benefits". In November 2011,
an IEA report entitled Deploying Renewables 2011 said "subsidies in
green energy technologies that were not yet competitive are justified
in order to give an incentive to investing into technologies with
clear environmental and energy security benefits". The IEA's report
disagreed with claims that renewable energy technologies are only
viable through costly subsidies and not able to produce energy
reliably to meet demand.
However, IEA's views are not universally accepted. Between 2010 and
2016, subsidies for wind were between 1.3¢ and 5.7¢ per kWh.
Subsidies for coal, natural gas and nuclear are all between 0.05¢ and
0.2¢ per kWh over all years. On a per-kWh basis, wind is subsidized
50 times as much as traditional sources. 
In the U.S., the wind power industry has recently increased its
lobbying efforts considerably, spending about $5 million in 2009 after
years of relative obscurity in Washington. By comparison, the
U.S. nuclear industry alone spent over $650 million on its lobbying
efforts and campaign contributions during a single ten-year period
ending in 2008.
Following the 2011 Japanese nuclear accidents, Germany's federal
government is working on a new plan for increasing energy efficiency
and renewable energy commercialization, with a particular focus on
offshore wind farms. Under the plan, large wind turbines will be
erected far away from the coastlines, where the wind blows more
consistently than it does on land, and where the enormous turbines
won't bother the inhabitants. The plan aims to decrease Germany's
dependence on energy derived from coal and nuclear power plants.
Environmental group members are both more in favor of wind power (74%)
as well as more opposed (24%). Few are undecided.
Surveys of public attitudes across
Europe and in many other countries
show strong public support for wind power. About 80% of
EU citizens support wind power. In Germany, where wind power has
gained very high social acceptance, hundreds of thousands of people
have invested in citizens' wind farms across the country and thousands
of small and medium-sized enterprises are running successful
businesses in a new sector that in 2008 employed 90,000 people and
generated 8% of Germany's electric power.
Bakker et al. (2012) discovered in their study that when residents did
not want the turbines located by them their annoyance was
significantly higher than those "that benefited economically from wind
turbines the proportion of people who were rather or very annoyed was
Although wind power is a popular form of energy generation, the
construction of wind farms is not universally welcomed, often for
In Spain, with some exceptions, there has been little opposition to
the installation of inland wind parks. However, the projects to build
offshore parks have been more controversial. In particular, the
proposal of building the biggest offshore wind power production
facility in the world in southwestern
Spain in the coast of Cádiz, on
the spot of the 1805 Battle of Trafalgar has been met with strong
opposition who fear for tourism and fisheries in the area, and
because the area is a war grave.
Which should be increased in Scotland?
In a survey conducted by Angus Reid Strategies in October 2007, 89 per
cent of respondents said that using renewable energy sources like wind
or solar power was positive for Canada, because these sources were
better for the environment. Only 4 per cent considered using renewable
sources as negative since they can be unreliable and expensive.
According to a Saint Consulting survey in April 2007, wind power was
the alternative energy source most likely to gain public support for
future development in Canada, with only 16% opposed to this type of
energy. By contrast, 3 out of 4 Canadians opposed nuclear power
A 2003 survey of residents living around Scotland's 10 existing wind
farms found high levels of community acceptance and strong support for
wind power, with much support from those who lived closest to the wind
farms. The results of this survey support those of an earlier Scottish
Executive survey 'Public attitudes to the Environment in Scotland
2002', which found that the Scottish public would prefer the majority
of their electric power to come from renewables, and which rated wind
power as the cleanest source of renewable energy. A survey
conducted in 2005 showed that 74% of people in
Scotland agree that
wind farms are necessary to meet current and future energy needs. When
people were asked the same question in a Scottish renewables study
conducted in 2010, 78% agreed. The increase is significant as there
were twice as many wind farms in 2010 as there were in 2005. The 2010
survey also showed that 52% disagreed with the statement that wind
farms are "ugly and a blot on the landscape". 59% agreed that wind
farms were necessary and that how they looked was unimportant.
Regarding tourism, query responders consider power pylons, cell phone
towers, quarries and plantations more negatively than wind farms.
Scotland is planning to obtain 100% of electric power from renewable
sources by 2020.
In other cases there is direct community ownership of wind farm
projects. The hundreds of thousands of people who have become involved
in Germany's small and medium-sized wind farms demonstrate such
Harris Poll reflects the strong support for wind power in
Germany, other European countries, and the U.S.
Opinion on increase in number of wind farms, 2010 Harris Poll
Oppose more than favour
Favour more than oppose
See also: Community debate about wind farms
Wind turbines such as these, in Cumbria, England, have been opposed
for a number of reasons, including aesthetics, by some sectors of the
Many wind power companies work with local communities to reduce
environmental and other concerns associated with particular wind
farms. In other cases there is direct community
ownership of wind farm projects. Appropriate government consultation,
planning and approval procedures also help to minimize environmental
risks. Some may still object to wind farms but,
according to The Australia Institute, their concerns should be weighed
against the need to address the threats posed by climate change and
the opinions of the broader community.
In America, wind projects are reported to boost local tax bases,
helping to pay for schools, roads and hospitals.
Wind projects also
revitalize the economy of rural communities by providing steady income
to farmers and other landowners.
In the UK, both the
National Trust and the Campaign to Protect Rural
England have expressed concerns about the effects on the rural
landscape caused by inappropriately sited wind turbines and wind
A panoramic view of the United Kingdom's Whitelee
Wind Farm with
Lochgoin Reservoir in the foreground.
Some wind farms have become tourist attractions. The Whitelee Wind
Farm Visitor Centre has an exhibition room, a learning hub, a café
with a viewing deck and also a shop. It is run by the Glasgow Science
In Denmark, a loss-of-value scheme gives people the right to claim
compensation for loss of value of their property if it is caused by
proximity to a wind turbine. The loss must be at least 1% of the
Despite this general support for the concept of wind power in the
public at large, local opposition often exists and has delayed or
aborted a number of projects. For example, there are
concerns that some installations can negatively affect TV and radio
reception and Doppler weather radar, as well as produce excessive
sound and vibration levels leading to a decrease in property
values. Potential broadcast-reception solutions include
predictive interference modeling as a component of site
selection. A study of 50,000 home sales near wind turbines
found no statistical evidence that prices were affected.
While aesthetic issues are subjective and some find wind farms
pleasant and optimistic, or symbols of energy independence and local
prosperity, protest groups are often formed to attempt to block new
wind power sites for various reasons.
This type of opposition is often described as NIMBYism, but
research carried out in 2009 found that there is little evidence to
support the belief that residents only object to renewable power
facilities such as wind turbines as a result of a "Not in my Back
Wind turbine and
Wind turbine design
Wind turbine aerodynamics
Typical wind turbine components:
Connection to the electric grid
Wind orientation control (Yaw control)
Electric or Mechanical Brake
Blade pitch control
Typical components of a wind turbine (gearbox, rotor shaft and brake
assembly) being lifted into position
Wind turbines are devices that convert the wind's kinetic energy into
electrical power. The result of over a millennium of windmill
development and modern engineering, today's wind turbines are
manufactured in a wide range of horizontal axis and vertical axis
types. The smallest turbines are used for applications such as battery
charging for auxiliary power. Slightly larger turbines can be used for
making small contributions to a domestic power supply while selling
unused power back to the utility supplier via the electrical grid.
Arrays of large turbines, known as wind farms, have become an
increasingly important source of renewable energy and are used in many
countries as part of a strategy to reduce their reliance on fossil
Wind turbine design is the process of defining the form and
specifications of a wind turbine to extract energy from the wind.
A wind turbine installation consists of the necessary systems needed
to capture the wind's energy, point the turbine into the wind, convert
mechanical rotation into electrical power, and other systems to start,
stop, and control the turbine.
In 1919 the German physicist
Albert Betz showed that for a
hypothetical ideal wind-energy extraction machine, the fundamental
laws of conservation of mass and energy allowed no more than 16/27
(59.3%) of the kinetic energy of the wind to be captured. This Betz
limit can be approached in modern turbine designs, which may reach 70
to 80% of the theoretical Betz limit.
The aerodynamics of a wind turbine are not straightforward. The air
flow at the blades is not the same as the airflow far away from the
turbine. The very nature of the way in which energy is extracted from
the air also causes air to be deflected by the turbine. In addition
the aerodynamics of a wind turbine at the rotor surface exhibit
phenomena that are rarely seen in other aerodynamic fields. The shape
and dimensions of the blades of the wind turbine are determined by the
aerodynamic performance required to efficiently extract energy from
the wind, and by the strength required to resist the forces on the
In addition to the aerodynamic design of the blades, the design of a
complete wind power system must also address the design of the
installation's rotor hub, nacelle, tower structure, generator,
controls, and foundation. Turbine design makes extensive use of
computer modelling and simulation tools. These are becoming
increasingly sophisticated as highlighted by a recent state-of-the-art
review by Hewitt et al. Further design factors must also be
considered when integrating wind turbines into electrical power grids.
Map of available wind power for the United States. Color codes
indicate wind power density class. (click to see larger)
Distribution of wind speed (red) and energy (blue) for all of 2002 at
the Lee Ranch facility in Colorado. The histogram shows measured data,
while the curve is the Rayleigh model distribution for the same
average wind speed.
Wind energy is the kinetic energy of air in motion, also called wind.
Total wind energy flowing through an imaginary surface with area A
during the time t is:
displaystyle E= frac 1 2 mv^ 2 = frac 1 2 (Avtrho )v^ 2 =
frac 1 2 Atrho v^ 3 ,
where ρ is the density of air; v is the wind speed; Avt is the volume
of air passing through A (which is considered perpendicular to the
direction of the wind); Avtρ is therefore the mass m passing through
"A". Note that ½ ρv2 is the kinetic energy of the moving air per
Power is energy per unit time, so the wind power incident on A (e.g.
equal to the rotor area of a wind turbine) is:
displaystyle P= frac E t = frac 1 2 Arho v^ 3 .
Wind power in an open air stream is thus proportional to the third
power of the wind speed; the available power increases eightfold when
the wind speed doubles.
Wind turbines for grid electric power
therefore need to be especially efficient at greater wind speeds.
Wind is the movement of air across the surface of the Earth, affected
by areas of high pressure and of low pressure. The global wind
kinetic energy averaged approximately 1.50 MJ/m2 over the period from
1979 to 2010, 1.31 MJ/m2 in the Northern Hemisphere with 1.70 MJ/m2 in
the Southern Hemisphere. The atmosphere acts as a thermal engine,
absorbing heat at higher temperatures, releasing heat at lower
temperatures. The process is responsible for production of wind
kinetic energy at a rate of 2.46 W/m2 sustaining thus the circulation
of the atmosphere against frictional dissipation. A global
1 km2 map of wind resources is housed at
http://irena.masdar.ac.ae/?map=103, based on calculations by the
Technical University of Denmark. Unlike 'static' wind
speed atlases which give a single average speed across multiple years,
tools such as
Renewables.ninja provide time-varying simulations of
wind speed and power output from different wind turbine models at
The total amount of economically extractable power available from the
wind is considerably more than present human power use from all
sources. Axel Kleidon of the Max Planck Institute in Germany,
carried out a "top down" calculation on how much wind energy there is,
starting with the incoming solar radiation that drives the winds by
creating temperature differences in the atmosphere. He concluded that
somewhere between 18 TW and 68 TW could be extracted.
Cristina Archer and
Mark Z. Jacobson presented a "bottom-up" estimate,
which unlike Kleidon's are based on actual measurements of wind
speeds, and found that there is 1700 TW of wind power at an altitude
of 100 metres over land and sea. Of this, "between 72 and 170 TW
could be extracted in a practical and cost-competitive manner".
They later estimated 80 TW. However research at Harvard
University estimates 1 Watt/m2 on average and 2–10 MW/km2 capacity
for large scale wind farms, suggesting that these estimates of total
global wind resources are too high by a factor of about 4.
The strength of wind varies, and an average value for a given location
does not alone indicate the amount of energy a wind turbine could
To assess prospective wind power sites a probability distribution
function is often fit to the observed wind speed data. Different
locations will have different wind speed distributions. The Weibull
model closely mirrors the actual distribution of hourly/ten-minute
wind speeds at many locations. The Weibull factor is often close to 2
and therefore a
Rayleigh distribution can be used as a less accurate,
but simpler model.
REpower 5 MW wind turbine under construction at Nigg fabrication yard
on the Cromarty Firth
London Array under construction in 2009
Sunrise at the Fenton
Wind Farm in Minnesota, United States.
Wind farm in Xinjiang, China
Scroby Sands wind farm
Scroby Sands wind farm from Great Yarmouth
A wind turbine blade on I-35 near Elm Mott, an increasingly common
sight in Texas
Erection of an
Enercon E70-4 in Germany.
Middelgrunden offshore wind park.
Wind Farm in
Çanakkale province, Turkey.
Wind power system in Ambewela, Sri Lanka.
Wind Farm in Jhimpir, Pakistan
Renewable energy portal
Sustainable development portal
Airborne wind turbine
Cost of electricity by source
List of countries by electricity production from renewable sources
List of wind turbine manufacturers
Lists of offshore wind farms by country
Lists of wind farms by country
Outline of wind energy
GA Mansoori, N Enayati, LB Agyarko (2016), Energy: Sources,
Utilization, Legislation, Sustainability, Illinois as Model State,
World Sci. Pub. Co., ISBN 978-981-4704-00-7
Renewable energy by country
^ For example, a 1 MW turbine with a capacity factor of 35% will
not produce 8,760 MW·h in a year (1 × 24 × 365), but only 1 ×
0.35 × 24 × 365 = 3,066 MW·h, averaging to
^ California is an exception.
^ a b "GWEC, Global
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Wind power delivers too much to ignore,
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Wind Power is an Effective Technology Archived 12
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