Wind farm in Neuenkirchen, Dithmarschen, Germany. Energy Portal Wind power is the conversion of wind energy into more useful forms, usually electricity using wind turbines. In 2005, worldwide capacity of wind-powered generators was 58,982 megawatts, their production making up less than 1% of world-wide electricity use. Although still a relatively minor source of electricity for most countries, it accounts for 23% of electricity use in Denmark, 4.3% in Germany and around 8% in Spain. Globally, wind power generation more than quadrupled between 1999 and 2005. Most modern wind power is generated in the form of electricity by converting the rotation of turbine blades into electrical current by means of an electrical generator. In windmills (a much older technology) wind energy is used to turn mechanical machinery to do physical work, like crushing grain or pumping water. Wind power is used in large scale wind farms for national electrical grids as well as in small individual turbines for providing electricity in isolated locations. Wind energy is abundant, renewable, widely distributed, clean, and mitigates the greenhouse effect if it is used to replace fossil-fuel-derived electricity. Contents 1 Cost and growth 2 Wind energy 2.1 Wind variability and turbine power 3 List of wind power availability 4 Turbine siting 4.1 Onshore 4.2 Offshore 4.3 Airborne 4.4 Vertical axis turbines 5 Utilization 5.1 Large scale 5.2 Small scale 6 Debate for and against wind power 6.1 Arguments of supporters 6.1.1 Pollution 6.1.2 Long-term potential 6.1.3 Coping with intermittency 6.1.4 Ecology 6.1.5 Economic feasibility 6.1.6 Aesthetics 6.2 Arguments of opponents 6.2.1 Economics 6.2.2 Yield 6.2.3 CO2 Emissions 6.2.4 Ecological Footprint 6.2.5 Scalability 6.2.6 Aesthetics 7 See also 8 References 9 External links 9.1 Technical 9.2 Political 9.3 Wind power projects 9.4 Academic institutions 10 Other (and unclassified) external links Cost and growth - The cost of wind-generated electric power has dropped substantially. Since 2004, according to some sources, the price in the United States is now lower than the cost of fuel-generated electric power, even without taking externalities into account.[1][2][3] In 2005, wind energy cost one-fifth as much as it did in the late 1990s, and that downward trend is expected to continue as larger multi-megawatt turbines are mass-produced.[4] A British Wind Energy Association report gives an average generation cost of onshore wind power of around 3.2 pence per kilowatt hour. [5] - Wind power is growing quickly, at about 38% in 2003,[6] up from 25% growth in 2002. In the United States, as of 2003, wind power was the fastest growing form of electricity generation on a percentage basis.[7] Wind energy Main article: Wind An estimated 1 to 3% of energy from the Sun that hits the earth is converted into wind energy. This is about 50 to 100 times more energy than is converted into biomass by all the plants on earth through photosynthesis. Most of this wind energy can be found at high altitudes where continuous wind speeds of over 160 km/h (100 mph) occur. Eventually, the wind energy is converted through friction into diffuse heat all through the earth's surface and atmosphere. The origin of wind is simple. The earth is unevenly heated by the sun resulting in the poles receiving less energy from the sun than the equator does. Also the dry land heats up (and cools down) more quickly than the seas do. The differential heating powers a global atmospheric convection system reaching from the earth's surface to the stratosphere which acts as a virtual ceiling. Wind variability and turbine power A Darrieus wind turbine. The power in the wind can be extracted by allowing it to blow past moving wings that exert torque on a rotor. The amount of power transferred is directly proportional to the density of the air, the area swept out by the rotor, and the cube of the wind speed. The power P available in the wind is given by: where P is in watts, ρ (density of air) is measured in kg/m³, D (turbine blade length) is in m, and v (velocity of wind) is in m/s. The mass flow of air that travels through the swept area of a wind turbine varies with the wind speed and air density. As an example, on a cool 15°C (59°F) day at sea level, air density is about 1.22 kilograms per cubic metre (it gets less dense with higher humidity). An 8 m/s breeze blowing through a 100 meter diameter rotor would move about 76,000 kilograms of air per second through the swept area. The kinetic energy of a given mass varies with the square of its velocity. Because the mass flow increases linearly with the wind speed, the wind energy available to a wind turbine increases as the cube of the wind speed. The power of the example breeze above through the example rotor would be about 2.5 megawatts. As the wind turbine extracts energy from the air flow, the air is slowed down, which causes it to spread out and diverts it around the wind turbine to some extent. Albert Betz, a German physicist, determined in 1919 that a wind turbine can extract at most 59% of the energy that would otherwise flow through the turbine's cross section. The Betz limit applies regardless of the design of the turbine. More recent work by Gorlov shows a theoretical limit of about 30% for propeller-type turbines.[8] Actual efficiencies range from 10% to 20% for propeller-type turbines, and are as high as 35% for three-dimensional vertical-axis turbines like Darrieus or Gorlov turbines. 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. Energy is the Betz limit through a 100 meter diameter circle facing directly into the wind. Total energy for the year through that circle was 15.4 gigawatt-hours. Windiness varies, and an average value for a given location does not alone indicate the amount of energy a wind turbine could produce there. To assess the climatology of wind speeds at a particular location, a probability distribution function is often fit to the observed data. Different locations will have different wind speed distributions. The distribution model most frequently used to model wind speed climatology is a two-parameter Weibull distribution because it is able to conform to a wide variety of distribution shapes, from gaussian to exponential. The Rayleigh model, an example of which is shown plotted against an actual measured dataset, is a specific form of the Weibull function in which the shape parameter equals 2, and very closely mirrors the actual distribution of hourly wind speeds at many locations. Because so much power is generated by higher windspeed, much of the average power available to a windmill comes in short bursts. The 2002 Lee Ranch sample is telling: half of the energy available arrived in just 15% of the operating time. The consequence of this is that wind energy is not dispatchable as for fuel-fired power plants; additional output cannot be supplied in response to load demand. - - Since wind speed is not constant, a wind generator's annual energy production is never as much as its nameplate rating 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. A well-sited wind generator will have a capacity factor of as much as 35%. This compares to typical capacity factors of 90% for nuclear plants, 70% for coal plants, and 30% for oil plants.[9] When comparing the size of wind turbine plants to fueled power plants, it is important to note that 1000 kW of wind-turbine potential power would be expected to produce as much energy in a year as approximately 500 kW of coal-fired generation. Though the short-term (hours or days) output of a wind-plant is not completely predictable, the annual output of energy tends to vary only a few percent points between years. - - When storage, such as with pumped hydroelectric storage, or other forms of generation are used to "shape" wind power (by assuring constant delivery reliability), commercial delivery represents a cost increase of about 25%, yielding viable commercial performance.[1] Electricity consumption can be adapted to production variability to some extent with Energy Demand Management and smart meters that offer variable market pricing over the course of the day. For example, municipal water pumps that feed a water tower do not need to operate continuously and can be restricted to times when electricity is plentiful and cheap. Consumers could choose when to run the dishwasher or charge an electric vehicle. List of wind power availability Many electric utility companies across the United States allow customers to sign up to have some or all of their electricity supplemented by alternative energy - wind in most cases. Here is a list of some places where customers can sign up for this. Colorado Fort Collins - Fort Collins Utilities, Wind Power Program Denver - Xcel Energy - Windsource Online Sign up Florida - Florida Power & Light - Sunshine Energy Midwest - Aliant Energy, Second Nature Program Minnesota North Saint Paul - Sign up for the "Green Power" program Oklahoma - OG&E - Wind Power Sign Up Wisconsin Madison - Madison Gas & Electric, Sign Up for Wind Power Washington Seattle - Seattle City Light, Green Up Program Oregon Portland - Portland General Electric, Clean Wind Turbine siting Map of available wind power over the United States. Color codes indicate wind power density class. As a general rule, wind generators are practical where the average wind speed is 10 mph or greater. Obviously, meteorology plays an important part in determining possible locations for wind parks, though it has great accuracy limitations. Meteorological wind data is not usually sufficient for accurate siting of a large wind power project. An 'ideal' location would have a near constant flow of non-turbulent wind throughout the year and would not suffer too many sudden powerful bursts of wind. The wind blows faster at higher altitudes because of the reduced influence of drag of the surface (sea or land) and the reduced viscosity of the air. The increase in velocity with altitude is most dramatic near the surface and is affected by topography, surface roughness, and upwind obstacles such as trees or buildings. Typically, the increase of wind speeds with increasing height follows a logarithmic profile that can be reasonably approximated by the wind profile power law, using an exponent of 1/7th, which predicts that wind speed rises proportionally to the seventh root of altitude. Doubling the altitude of a turbine, then, increases the expected wind speeds by 10% and the expected power by 34%.citation needed] Wind farms or wind parks often have many turbines installed. Since each turbine extracts some of the energy of the wind, it is important to provide adequate spacing between turbines to avoid excess energy loss. Where land area is sufficient, turbines are spaced three to five rotor diameters apart perpendicular to the prevailing wind, and five to ten rotor diameters apart in the direction of the prevailing wind, to minimize efficiency loss. The "wind park effect" loss can be as low as 2% of the combined nameplate rating of the turbines. Utility-scale wind turbine generators have minimum temperature operating limits which restrict the application in areas that routinely experience temperatures less than −20°C. Wind turbines must be protected from ice accumulation, which can make anemometer readings inaccurate and which can cause high structure loads and damage. Some turbine manufacturers offer low-temperature packages at a few percent extra cost, which include internal heaters, different lubricants, and different alloys for structural elements, to make it possible to operate the turbines at lower temperatures. If the low-temperature interval is combined with a low-wind condition, the wind turbine will require station service power, equivalent to a few percent of its output rating, to maintain internal temperatures during the cold snap. For example, the St. Leon, Manitoba project has a total rating of 99 MW and is estimated to need up to 3 MW (around 3% of capacity) of station service power a few days a year for temperatures down to −30°C. This factor affects the economics of wind turbine operation in cold climates.citation needed] Onshore Wind turbines near Walla Walla in Washington Onshore turbine installations tend to be on ridgelines. This is done to exploit the so-called topographic acceleration. The hill or ridge causes the wind to accerate as it is forced over it. The additial wind speeds gained in this way make large differences to the amount of energy that produced. Great attention must be paid to the exact positions of the turbines (a process known as micro-siting) because a difference of 30 m can sometimes mean a doubling in output. Local winds are often monitored for a year or more with anemometers and detailed wind maps constructed before wind generators are installed. For smaller installations where such data collection is too expensive or time consuming, the normal way of prospecting for wind-power sites is to directly look for trees or vegetation that are permanently "cast" or deformed by the prevailing winds. Another way is to use a wind-speed survey map, or historical data from a nearby meteorological station, although these methods are less reliable. Sea shores also tend to be windy areas and good sites for turbine installation, because a primary source of wind is convection from the differential heating and cooling of land and sea over the course of day and night. Winds at sea level carry somewhat more energy than winds of the same speed in mountainous areas because the air at sea level is more dense. Wind farm siting can sometimes be highly controversial, particularly as the hilltop, often coastal sites preferred are often picturesque and environmentally sensitive (for instance, having substantial bird life). Local residents in a number of potential sites have strongly opposed the installation of wind farms, and political support has resulted in the blocking of construction of some installations [10]. Offshore Wind blows briskly and smoothly over water since there are no obstructions. The large and slow turning turbines of this offshore wind farm near Copenhagen take advantage of the moderate yet constant breezes here. Offshore wind turbines cause less aesthetic controversy since they often cannot be seen from the shore. Because there are fewer obstacles and stronger winds, such turbines also don´t need to be built as high into the air. However, offshore turbines are more inaccessible and offshore conditions are harsh, abrasive, and corrosive, thereby increasing the costs of operation and maintenance compared to onshore turbines. In areas with extended shallow continental shelves and sand banks (such as Denmark), turbines are reasonably easy to install, and give good service. At the site shown, the wind is not especially strong but is very consistent. The largest offshore wind turbines in the world are seven 3.6 MW rated machines off the east coast of Ireland about sixty kilometres south of Dublin. The turbines are located on a sandbank approximately ten kilometres from the coast that has the potential for the installation of 500 MW of generation capacity. As of 2006, the largest offshore wind farm is the Nysted Offshore Wind Farm at Rødsand, located about ten kilometres south of Nysted and thirteen kilometres west of Gedser Denmark. The wind farm consists of seventy two turbines of 2.3 MW, which produces 165.6 MW of power at rated wind speed.[11]. Three offshore wind farms in the United Kingdom are currently operating, North Hoyle (30 x 2 MW), Scroby Sand (30 x 2 MW) and Kentish flat (30 x 3 MW). Another offshore wind farm, Barrow (30 x 3 MW), is under construction. Under the energy policy of the United Kingdom further offshore facilities are feasible and expected by the year 2010. Not all offshore wind farms have been without siting controversies, such as the proposed Cape Wind offshore development in the United States and the Havsul development in Norway. Airborne Main article: Airborne wind turbine Wind turbines might also be flown in high speed winds at altitude[12], although no such systems currently exist in the marketplace. An Ontario company, Magenn Power, Inc., is attempting to commercialize tethered aerial turbines suspended with helium[13] Vertical axis turbines A prototype of vertical axis wind turbine is the italian project called "Kitegen". It is an innovative plan (still in phase of construction) that consists in one wind farm with a vertical spin axis, and employs kites to exploit high-altitude winds. The Kite Wind Generator (KWG) or KiteGen is claimed to eliminate all the static and dynamic problems that prevent the increase of the power (in terms of dimensions) obtainable from the traditional horizontal axis wind turbine generators. According to its developers, a one GigaWatt installation will be 1/40 the cost of the corresponding nuclear powerplant. The project kitegen has received 15 million euro financing from the Italian state. It will begun with a 1 MW prototype and then with the planning of a power kitegen of 20 MW. citation needed] Utilization Large scale Total installed windpower capacity (end of year & latest estimates)[14] Capacity (MW) Rank Nation Latest 2005 2004 1 Germany 19,267 18,428 16,629 2 Spain 10,941 10,027 8,263 3 USA 9,972 9,149 6,725 4 India 5,340 4,430 3,000 5 Denmark 3,128 3,124 6 Italy 1,717 1,265 7 United Kingdom 1,937 1,353 888 8 China 1,260 764 9 Netherlands 1,219 1,078 10 Japan 1,040 896 11 Portugal 1,022 522 12 Austria 819 606 13 France 918 757 386 14 Canada 1,049 683 444 15 Greece 573 473 16 Australia 817 572 379 17 Sweden 510 452 18 Ireland 496 339 19 Norway 270 270 20 New Zealand 168 168 21 Belgium 167 95 22 Egypt 145 145 23 South Korea 119 23 24 Taiwan 103 13 25 Finland 82 82 26 Poland 107 73 63 27 Ukraine 73 69 28 Costa Rica 70 70 29 Morocco 64 54 30 Luxembourg 35 35 31 Iran 32 25 32 Estonia 30 3 33 Philippines 29 29 34 Brazil 79 29 24 35 Czech Republic 28 17 36 Turkey 50 20  ? World total ~63,000 58,982 47,671 There are many thousands of wind turbines operating, with a total capacity of 58,982 MW of which Europe accounts for 69% (2005). The average output of one megawatt of wind power is equivalent to the average consumption of about 160 American households. Wind power was the most rapidly-growing means of alternative electricity generation at the turn of the century and world wind generation capacity more than quadrupled between 1999 and 2005. 90% of wind power installations are in the US and Europe, but the share of the top five countries in terms of new installations fell from 71% in 2004 to 55% in 2005. By 2010, World Wind Energy Association expects 120,000 MW to be installed worldwide.[14] Germany, Spain, the United States, India and Denmark have made the largest investments in wind generated electricity. Denmark is prominent in the manufacturing and use of wind turbines, with a commitment made in the 1970s to eventually produce half of the country's power by wind. Denmark generates over 20% of its electricity with wind turbines, the highest percentage of any country and is fifth in the world in total power generation (which can be compared with the fact that Denmark is 56th on the general electricity comsumption list). Denmark and Germany are leading exporters of large (0.66 to 5 MW) turbines. Wind accounts for 1% of the total electricity production on a global scale (2005). Germany is the leading producer of wind power with 32% of the total world capacity in 2005 (6% of German electricity); the official target is that by 2010, renewable energy will meet 12.5% of German electricity needs - it can be expected that this target will be reached even earlier. Germany has 16,000 wind turbines, mostly in the north of the country - including three of the biggest in the world, constructed by the companies Enercon (4.5 MW), Multibrid (5 MW) and Repower (5 MW). Germany's Schleswig-Holstein province generates 25% of its power with wind turbines. Spain and the United States are next in terms of installed capacity. In 2005, the government of Spain approved a new national goal for installed wind power capacity of 20,000 MW by 2012. According to trade journal Windpower Monthly, however, in 2006 they abruptly halted subsidies and price supports for wind power. According to the American Wind Energy Association, wind generated enough electricity to power 0.4% (1.6 million households) of total electricity in US, up from less than 0.1% in 1999. In 2005, both Germany and Spain have produced more electricity from wind power than from hydropower plants. US Department of Energy studies have concluded wind harvested in just three of the fifty U.S. states could provide enough electricity to power the entire nation, and that offshore wind farms could do the same job.[1] Wind power could grow by 50% in the U.S. in 2006.[15] India ranks 4th in the world with a total wind power capacity of 5,340 MW. Wind power generates 3% of all electricity produced in India. The World Wind Energy Conference in New Delhi in November 2006 will give additional impetus to the Indian wind industry.[14] In December 2003, General Electric installed the world's largest offshore wind turbines in Ireland, and plans are being made for more such installations on the west coast, including the possible use of floating turbines. On August 15, 2005, China announced it would build a 1000-megawatt wind farm in Hebei for completion in 2020. China reportedly has set a generating target of 20,000 MW by 2020 from renewable energy sources - it says indigenous wind power could generate up to 253,000 MW. Following the World Wind Energy Conference in November 2004, organised by the Chinese and the World Wind Energy Association, a Chinese renewable energy law was adopted. In late 2005, the Chinese government increased the official wind energy target for the year 2020 from 20 GW to 30 GW.citation needed] Another growing market is Brazil, with a wind potential of 143 GW.[16] The federal government has created an incentive program, called Proinfa,[17] to build production capacity of 3300 MW of renewable energy for 2008, of which 1422 MW through wind energy. The program seeks to produce 10% of Brazilian electricity through renewable sources. Brazil produced 320 TWh in 2004. France recently annonced a very ambitious target of 12 500 MW installed by 2010. Over the 6 years from 2000-2005, Canada experienced rapid growth of wind capacity - moving from a total installed capacity of 137 MW to 943 MW, and showing a growth rate of 38% and rising.[18] This growth was fed by provincial measures, including installation targets, economic incentives and political support. For example, the government of the Canadian province of Ontario announced on 21 March 2006 that it will introduce a feed-in tariff for wind power, referred to as 'Standard Offer Contracts', which may boost the wind industry across the entire country.[19] In the Canadian province of Quebec, the state-owned hydroelectric utility plans to generate 2000 MW from wind farms by 2013.[20] Small scale Main article: Small wind turbine This rooftop-mounted urban wind turbine charges a 12 volt battery and runs various 12 volt appliances within the building on which it is installed. Wind turbines have been used for household electricity generation in conjunction with battery storage over many decades in remote areas. Household generator units of more than 1 kW are now functioning in several countries. To compensate for the varying power output, grid-connected wind turbines may utilise some sort of grid energy storage. Off-grid systems either adapt to intermittent power or use photovoltaic or diesel systems to supplement the wind turbine. Wind turbines range from small four hundred watt generators for residential use to several megawatt machines for wind farms and offshore. The small ones have direct drive generators, direct current output, aeroelastic blades, lifetime bearings and use a vane to point into the wind; while the larger ones generally have geared power trains, alternating current output, flaps and are actively pointed into the wind. Direct drive generators and aeroelastic blades for large wind turbines are being researched and direct current generators are sometimes used. In urban locations, where it is difficult to obtain large amounts of wind energy, smaller systems may still be used to run low power equipment. Distributed power from rooftop mounted wind turbines can also alleviate power distribution problems, as well as provide resilience to power failures. Equipment such as parking meters or wireless internet gateways may be powered by a wind turbine that charges a small battery, replacing the need for a connection to the power grid and/or maintaining service despite possible power grid failures. Small-scale wind power in rural Indiana. Small scale turbines are available that are approximately 7 feet (2 m) in diameter and produce 900 watts. Units are lightweight, e.g. 16 kilograms (35 lbs), allowing rapid response to wind gusts typical of urban settings and easy mounting much like a television antenna. It is claimed that they are inaudible even a few feet under the turbine.citation needed] Dynamic braking regulates the speed by dumping excess energy, so that the turbine continues to produce electricity even in high winds. The dynamic braking resistor may be installed inside the building to provide heat (during high winds when more heat is lost by the building, while more heat is also produced by the braking resistor). The proximal location makes low voltage (12 volt, or the like) energy distribution practical. An additional benefit is that owners become more aware of electricity consumption, possibly reducing their consumption down to the average level that the turbine can produce. According to the World Wind Energy Association, it is difficult to assess the total number or capacity of small-scaled wind turbines, but in China alone, there are roughly 300,000 small-scale wind turbines generating electricity.[14] Debate for and against wind power Arguments for and against wind power are listed below. Arguments of supporters Erection of an Enercon E70-4 Supporters of wind energy state that: Pollution Wind power is a renewable resource, which means using it will not deplete the earth's supply of fossil fuels. It also is a clean energy source, and operation does not produce carbon dioxide, sulfur dioxide, mercury, particulates, or any other type of air pollution, as do conventional fossil fuel power sources. During manufacture of the wind turbine, however, steel, concrete, aluminum and other materials will have to be made and transported using energy-intensive processes, generally using fossil energy sources. Nevertheless, the energy used for manufacture of a wind turbine is earned back in four to six months of operation. Long-term potential Wind's long-term theoretical potential is much greater than current world energy consumption. The most comprehensive study to date[21] found the potential of wind power on land and near-shore to be 72 TW (~54,000 Mtoe), or over five times the world's current energy use and 40 times the current electricity use. The potential takes into account only locations with Class 3 (mean annual wind speeds ≥ 6.9 m/s at 80 m) or better wind regimes, which includes the locations suitable for low-cost (0.03–0.04 $/kWh) wind power generation and is in that sense conservative. It assumes 6 turbines per square km for 77-m diameter, 1,5 MW turbines on roughly 13% of the total land area. This potential assumes a capacity factor of 48% and does not take into account the practicality of reaching the windy sites or of transmission (including 'choke' points) or of competing land uses or of wheeling power over large distances or of switching to wind power. To determine the more realistic technical potential it is essential how large a fraction of this land could be made available to wind power. In the 2001 IPCC report, it is assumed that a use of 4% - 10% of that land area would be practial. Even so, the potential comfortably exceeds current world electricity demand. Offshore resources experience mean wind speeds ~90% greater than that of land, so offshore resources could contribute about seven times more energy than land.[22][23] This number could also increase with higher altitude or airborne wind turbines.[24] Coping with intermittency As the fraction of energy produced by wind ("penetration") increases, different technical and economic factors affect the need for grid energy storage facilities, demand side management, and/or other management of system load. Large networks, connected to multiple wind plants at widely separated geographic locations, may accept a higher penetration of wind than small networks or those without storage systems or economical methods of compensating for the variability of wind. In systems with significant amounts of existing pumped storage, hydropower or other peaking power plants, such as natural gas-fired power plants, this proportion may be higher. Isolated, relatively small systems with only a few wind plants may only be stable and economic with a lower fraction of wind energy (e.g. Ireland). On most large power systems a moderate proportion of wind generation can be connected without the need for storage. For larger proportions, storage may be economically attractive or even technically necessary. The profile of other generation facilities in the system (nuclear, coal, natural gas, hydro, etc.) will also influence the potential need for storage. At present, there are few large systems (for example, at the national or regional level) with sufficiently high wind generation to drive demand for storage, and discussion of the issue and potential upper limits for wind penetration remain largely hypothetical. Long-term storage of electrical energy involves substantial capital costs, space for storage facilities, and some portion of the stored power will be lost during conversion and transmission. The percentage retrievable from stored power is called the "efficiency of storage." The cost incurred to "shape" intermittent wind power for reliable delivery is about a 20% premium for most wind applications on large grids, but approaches 50% of the cost of generation when wind comprises more than 70% of the local grid's input power. See: Grid energy storage Cement works in New South Wales, Australia. Energy-intensive process like this could utilize burst electricity from wind. Electricity demand is variable but generally very predictable on larger grids; errors in demand forecasting are typically no more than 2%. Because conventional powerplants can drop off the grid within a few seconds, for example due to equipment failures, in most systems the output of some coal or gas powerplants is intentionally part-loaded to follow demand and to replace rapidly lost generation. The ability to follow demand (by maintaining constant frequency) is termed "response." The ability to quickly replace lost generation, typically within timescales of 30 seconds to 30 minutes, is termed "spinning reserve." Nuclear power plants in contrast are not very flexible and are not intentionally part-loaded. A power plant that operates in a steady fashion, usually for many days continuously, is termed a "base load" plant. Generally thermal plants running as "peaking" plants will be less efficient than if they were running as base load. Hydroelectric facilities with storage capacity (such as the traditional dam configuration) may be operated as base load or peaking plants, and complement high levels of wind penetration. What happens in practice therefore is that as the power output from wind varies, part-loaded conventional plants, which must be there anyway to provide response (due to continuously changing demand) and reserve , adjust their output to compensate; they do this in response to small changes in the frequency (nominally 50 or 60 Hz) of the grid. In this sense wind acts like "negative" load or demand. The maximum proportion of wind power allowable in a power system will thus depend on many factors, including the size of the system, the attainable geographical diversity of wind, the conventional plant mix (coal, gas, nuclear, hydroelectric) and seasonal load factors (heating in winter, air-conditioning in summer) and their statistical correlation with wind output. For most large systems the allowable penetration fraction (wind nameplate rating divided by system peak demand) is thus at least 15% without the need for any energy storage whatsoever. Note that the interconnected electrical system may be much larger than the particular country or state (e.g. Denmark, California) being considered. It should also be borne in mind that wind output, especially from large numbers of turbines/farms can be predicted with a fair degree of confidence many hours ahead using weather forecasts. The allowable penetration may of course be further increased by increasing the amount of part-loaded generation available, or by using energy storage facilities, although if purpose-built for wind energy these may significantly increase the overall cost of wind power. Existing European hydroelectric power plants can store enough energy to supply one month's worth of European electricity consumption. Improvement of the international grid would allow using this in the relatively short term at low cost, as a matching variable complementary source to wind power. Excess wind power could even be used to pump water up into collection basins for later use. In practice, Denmark's system is well-integrated with the hydro-electric dominated Norwegian system, and Norwegian hydropower is used to balance fluctuations and shortfalls in Denmark; on occasion, Denmark exports electricity to Norway when generation is higher than demand (thereby increasing stored hydropower). Increased wind penetration may raise the value of existing peaking or storage facilities and particularly hydroelectric plants, as their ability to compensate for wind's variability will be under greater demand. Energy Demand Management or Demand-Side Management refers to the use of communication and switching devices which can release deferrable loads quickly to correct supply/demand imbalances. Incentives can be created for the use of these systems, such as favorable rates or capital cost assistance, encouraging consumers with large loads to take advantage of renewable energy by adjusting their loads to coincide with resource availability. For example, pumping water to pressurize municipal water systems is an electricity intensive application that can be performed when electricity is available.[25] Real-time variable electricity pricing can encourage all users to reduce usage when the renewable sources happen to be at low production. In energy schemes with a high penetration of wind energy, secondary loads, such as desalination plants and electric boilers may be encouraged because their output (water and heat) can be stored. The utilization of "burst electricity", where excess electricity is used on windy days for opportunistic purposes greatly improves the economic efficiency of wind turbine schemes. An ice storage device has been invented which allows cooling energy to be consumed during resource availability, and dispatched as air conditioning during peak hours. Multiple wind farms spread over a wide geographic area and gridded together produce power much more constantly. Electricity produced from solar energy could be a counter balance to the fluctuating supplies generated from wind. It tends to be windier at night and during cloudy or stormy weather, so there is likely to be more sunshine when there is less wind. Wind speeds tend to be higher in the winter and at night, so the appropriateness of wind power in high concentrations may crucially depend on the prevalence of air conditioning in a given jurisdiction. Wind power may be weakest in the hot summer months, and particularly during the day when air conditioning demand is highest. Conversely, systems where heat is electrical may be well-suited to higher penetration of wind power. Ecology Because it uses energy already present in the atmosphere, and can displace fossil-fuel generated electricity (with its accompanying carbon dioxide emissions), wind power mitigates global warming. While wind turbines might impact the numbers of some bird species, conventionally fueled power plants could wipe out hundreds or even thousands of the world's species through climate change, acid rain, and pollution. Energy payback ratio (ratio of energy produced compared to energy expended in construction and operation) for wind turbines has been estimated in one report to be between 17 and 39 (i.e. over its life-time a wind turbine produces 17-39 times as much energy as is needed for its manufacture, construction, operation and decommissioning). A similar Danish study determined the payback ratio to be 80, which means that a wind turbine system pays back the energy invested within approximately 3 months. [26] This is to be compared with payback ratios of 11 for coal power plants and 16 for nuclear power plants, though such figures do not take into account the energy content of the fuel itself, which would lead to a negative energy 'payback'.[27] Unlike fossil fuel or nuclear power stations, which circulate or evaporate large amounts of water for cooling, wind turbines do not need water to generate electricity. Studies show that the number of birds killed by wind turbines is negligible compared to the amount that die as a result of other human activities such as traffic, hunting, power lines and high-rise buildings and especially the environmental impacts of using non-clean power sources. For example, in the UK, where there are several hundred turbines, about one bird is killed per turbine per year; 10 million per year are killed by cars alone.[28] In the United States, turbines kill 70,000 birds per year, compared to 57 million killed by cars and 97.5 million killed by collisions with plate glass.[29] Another study suggests that migrating birds adapt to obstacles; those birds which don't modify their route and continue to fly through a wind farm are capable of avoiding the large offshore windmills,[30] at least in the low-wind non-twilight conditions studied. In the UK, the Royal Society for the Protection of Birds (RSPB) concluded that "The available evidence suggests that appropriately positioned wind farms do not pose a significant hazard for birds."[31] It notes that climate change poses a much more significant threat to wildlife, and therefore supports wind farms and other forms of renewable energy. Clearing of wooded areas is often unnecessary, as the practice of farmers leasing their land out to companies building wind farms is common. Farmers receive annual lease payments of two thousand to five thousand dollars per turbine.[32] The land can still be used for farming and cattle grazing. The ecological and environmental costs of wind plants are paid by those using the power produced, with no long-term effects on climate or local environment left for future generations. Less than 1% of the land would be used for foundations and access roads, the other 99% could still be used for farming.[33] Turbines can be sited on land unused in techniques such as center-pivot irrigation. Economic feasibility Conventional and nuclear power plants receive massive amounts of direct and indirect governmental subsidies. If a comparison is made on real production costs, wind energy is competitive in many cases. If the full costs (environmental, health, etc.) are taken into account, wind energy is competitive in most cases. Furthermore, wind energy costs are continuously decreasing due to technology development and scale enlargement. Nuclear power plants receive special immunity from the disasters they may cause, which prevents victims from recovering the cost of their continued health care from those responsible, even in the case of criminal malfeasance. Conventional and nuclear plants also have sudden unpredictable outages (see above). Statistical analysis shows that 1000 MW of wind power can replace 300 MW of conventional power. Aesthetics Wind power is nothing new. Windmills at La Mancha, Spain. Improvements in blade design and gearing have quietened modern turbines to the point where a normal conversation can be held underneath one Newer wind farms have more widely spaced turbines due to the greater power of the individual wind turbines, and so look less cluttered Wind turbines can be positioned alongside motorways, significantly reducing aesthetic concerns The aesthetics of wind turbines have been compared favourably to those of pylons from conventional power stations Areas under windfarms can be used for farming, and are protected from development Offshore sites have on average a higher energy yield than onshore sites, and often cannot be seen from the shore. Arguments of opponents Some of the over 4000 wind turbines at Altamont Pass, in California. Developed during a period of tax incentives in the 1980s, this wind farm has more turbines than any other in the United States. These turbines are only a few tens of kilowatts each. Economics To compete with traditional sources of energy, wind power often receives financial incentives. In the United States, wind power receives a tax credit currently of 1.9 cents per kilowatt-hour produced, with a yearly inflationary adjustment. 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." Countries such as Canada and Germany also provide tax credits and other incentives for wind turbine construction. Many potential sites for wind farms are far from demand centers, requiring substantially more money to construct new transmission lines and substations. Yield The goals of renewable energy development are reduction of reliance on fossil and nuclear fuels, reduction of greenhouse gas and other emissions, and establishment of more sustainable sources of energy. Critics question wind energy's ability to significantly move society towards these goals. They point out that 20-30% annual load factor is typical for wind facilities. The intermittent and non-dispatchable nature of wind turbine power requires that "spinning reserves" are kept burning for supply security. The fluctuation in wind power requires more frequent load ramping of such plants to maintain grid system frequency. This can force operators to run conventional plants below optimal thermal efficiency, resulting in greater emissions. A recent European Nuclear Society study estimates that the equivalent of one third of energy saved from wind generation is lost to these inefficiencies.citation needed] CO2 Emissions Electric power production is only part (about 39% in the USA[34]) of a country's energy use, so wind power alone does little to mitigate the larger part of the effects of energy use (except with a potential transition to electric or hydrogen vehicles). For example, despite more than doubling the installed wind power capacity in the U.K. from 2002 to 2004, wind power contributed less than 1% of the national electricity supply,[5] and that country's CO2 emissions continued to rise in 2002 and 2003 (Department of Trade and Industry). Six of the U.K.'s nuclear reactors were closed in this period.[35] Groups such as the UN's Intergovernmental Panel on Climate Change state that the desired mitigation goals can be achieved at lower cost and to a greater degree by continued improvements in general efficiency — in building, manufacturing, and transport — than by wind power.[36] Ecological Footprint The clearing of trees around tower bases may be necessary to enable installation. This is an issue for potential sites on mountain ridges, such as in the northeastern U.S.[37]. Wind turbines should ideally be placed about ten times their diameter apart in the direction of prevailing winds and five times their diameter apart in the perpendicular direction for minimal losses due to wind park effects. As a result, wind turbines require roughly 0.1 square kilometres of unobstructed land per megawatt of nameplate capacity. A wind farm that produces the energy equivalent of a conventional power plant might have turbines spread out over an area of approximately 200 square kilometres. A wind turbine at Greenpark, Reading, England Some windmills kill birds, especially birds of prey.[38] More recent siting generally takes into account known bird flight patterns, but some paths of bird migration, particularly for birds that fly by night, are unknown. A Danish survey in 2005 (Biology Letters 2005:336) showed that less than 1% of migrating birds passing a wind farm in Rønde, Denmark, got close to collision, though the site was studied only during low-wind non-twilight conditions. A survey at Altamont Pass, California, conducted by a California Energy Commission in 2004 showed that turbines killed between 1,766 and 4,721[39] birds annually (881 to 1,300 of which were birds of prey). Radar studies of proposed sites in the eastern U.S. have shown that migrating songbirds fly well within the reach of large modern turbine blades. A wind farm in Norway's Smøla islands is reported to have destroyed a colony of sea eagles, according to the British Royal Society for the Protection of Birds.[40] The society said turbine blades killed nine of the birds in a 10 month period, including all three of the chicks that fledged that year. Norway is regarded as the most important place for white-tailed eagles. The numbers of bats killed by existing facilities has troubled even industry personnel.[41] A six-week study in 2004 estimated that over 2200 bats were killed by 63 turbines at two sites in the eastern U.S.[42] This study suggests some site locations may be particularly hazardous to local bat populations, and that more research is urgently needed. Migratory bat species appear to be particularly at risk, especially during key movement periods (spring and more importantly in fall). Lasiurines such as the hoary bat (Lasiurus cinereus), and red bat (Lasiurus borealis) along with semi-migratory silver-haired bats (Lasionycteris noctivagans) appear to be most vulnerable at North American sites. Almost nothing is known about current populations of these species and the impact on bat numbers as a result of mortality at windpower locations. Scalability To meet the energy demands worldwide in the future in a sustainable way, a much larger number of turbines than we have today will be required. Naturally this will affect more people and wildlife habitat. In Denmark, wind power now accounts for close to 20% of electricity consumption [43] and a recent poll of Danes show that 90% want more wind power installed [44]. Danish wind power is dependent on the import and export of electricity to Germany, Sweden, and Norway at short notice when wind generated power is less than or greater than current demand, respectively. As its neighbors increase their own wind energy, this will not be as simple a solution. Aesthetics Recorded experience that wind turbines are noisy and visually intrusive creates resistance to the establishment of land-based wind farms in most places. Moving the turbines far offshore mitigates the problem, but offshore wind farms are more expensive to maintain and there is an increase in transmission loss due to longer distances of power lines. Some residents near windmills complain of "shadow flicker," which is the alternating pattern of sun and shade caused by a rotating windmill casting a shadow over residences. Efforts are made when siting turbines to avoid this problem. Large wind towers require strobe lights, which "pollute" the rural night sky. See also Power Generation Fossil fuel power and petro-free Hydropower Nuclear Power Solar power and nuclear residues. Solar updraft tower Steam engine Green Energy Green energy Green tax shift Grid energy storage Renewable energy Nuclear power phase-out Wind Windmill Wind farm Wind turbine By country Wind power in the United Kingdom References ^ a b c Mitchell, Chris (March 23, 2006). Price of Wind-Generated Electricity Plummeting. Retrieved on 2006-04-21. ^ Chakrabarty, Gargi (March 27, 2004). Powering up. Rocky Mountain News. Retrieved on 2004-04-05. (Internet Archive version) ^ E-Letter responses to: The Real Cost of Wind Energy. Science. Retrieved on 2006-04-21. ^ Helming, Troy (February 2, 2004). Uncle Sam's New Year's Resolution. Retrieved on 2006-04-21. ^ a b BWEA report on onshore wind costs ^ Alternate Power: A Change Is In The Wind. Business Week (July 4, 2005). Retrieved on 2006-04-21. ^ Renewable Energy Trends 2003 (PDF). DOE/EIA (July 2004). Retrieved on 2006-04-21. ^ Gorban, Alexander N. (December 2001). "Limits of the Turbine Efficiency for Free Fluid Flow". Journal of Energy Resources Technology 123: 311-317. Retrieved on 2006-04-21. ^ {{cite web - | last = Nuclear Energy Institute - | title = Nuclear Facts - | url = http://www.nei.org/doc.asp?catnum=2&catid=106 - | accessdate = July 23rd, 2006 }} ^ Hogan, Jesse. "Fury over wind farm decision", The Age, 2006-04-05. Retrieved on 2006-08-18. ^ Nysted offshore wind farm. E2. Retrieved on 2006-06-10. ^ David Cohn. Windmills in the Sky. Wired News: Windmills in the Sky. San Francisco: Wired News. Retrieved on July 28, 2006. ^ Magenn Power Inc. corporate website. Retrieved on August 18, 2006. ^ a b c d the World Wind Energy Association (WWEA) web site. Retrieved on 2006-04-21. ^ Aslam, Abid (31 March 2006). Problem: Foreign Oil, Answer: Blowing in the Wind?. OneWorld US. Retrieved on 2006-04-21. ^ Atlas do Potencial Eólico Brasileiro. Retrieved on 2006-04-21. ^ Eletrobrás - Centrais Elétricas Brasileiras S.A - Projeto Proinfa. Retrieved on 2006-04-21. ^ Wind Energy: Rapid Growth (PDF). Canadian Wind Energy Association. Retrieved on 2006-04-21. ^ Standard Offer Contracts Arrive In Ontario. Ontario Sustainable Energy Association (March 21, 2006). Retrieved on 2006-04-21. ^ Call for Tenders A/O 2005-03: Wind Power 2,000 MW. Hydro-Québec. Retrieved on 2006-04-21. ^ Archer, Cristina L.; Mark Z. Jacobson. Evaluation of global wind power. Retrieved on 2006-04-21. ^ Archer, Cristina L.; Mark Z. Jacobson. Evaluation of global wind power. Retrieved on 2006-04-21. ^ Global Wind Map Shows Best Wind Farm Locations. Environment News Service (May 17, 2005). Retrieved on 2006-04-21. ^ Cohn, David (Apr 06, 2005). Windmills in the Sky. Wired News. Retrieved on 2006-04-21. ^ 2005 Integrated Energy Policy Report. California Energy Commission (November 21, 2005). Retrieved on 2006-04-21. ^ Danish Wind Industry Association. Danis Wind Turbine Manufacturer's Association (December 1997). Retrieved on 2006-05-12. ^ Net Energy Payback and CO2 Emissions from Wind-Generated Electricity in the Midwest. S.W.White & G.L.Klucinski - Fusion Technology Institute University of Wisconsin (December 1998). Retrieved on 2006-05-12. ^ Birds. Retrieved on 2006-04-21. ^ Lomborg, Bjørn (2001). The Skeptical Environmentalist. New York City: Cambridge University Press. ^ (18 June 2005). "Wind turbines a breeze for migrating birds". New Scientist (2504): 21. Retrieved on 2006-04-21. ^ Wind farms. Royal Society for the Protection of Birds (14 September 2005). Retrieved on 2006-04-21. ^ RENEWABLE ENERGY - Wind Power’s Contribution to Electric Power Generation and Impact on Farms and Rural Communities (GAO-04-756) (PDF). United States Government Accountability Office (September 2004). Retrieved on 2006-04-21. ^ Wind energy Frequently Asked Questions. British Wind Energy Association. Retrieved on 2006-04-21. ^ Annual Energy Review 2004 Report No. DOE/EIA-0384(2004). Energy Information Administration (August 15, 2005). Retrieved on 2006-04-21. ^ Nuclear Power in the United Kingdom - Briefing Paper # 84. Uranium Information Centre Ltd (December 2005). Retrieved on 2006-04-21. ^ Wind and the Mitigation of CO2 Emissions -- The Global Picture.} ^ Forest clearance for Meyersdale, Pa., wind power facility ^ The negative effects of windfarms on birds and other wildlife: articles by Mark Duchamp ^ Developing Methods to Reduce Bird Mortality In the Altamont Pass Wind Resource Area ^ Royal Society for the Protection of Birds: Wind farm strikes at eagle stronghold ^ Caution Regarding Placement of Wind Turbines on Wooded Ridge Tops (PDF). Bat Conservation International (4 January 2005). Retrieved on 2006-04-21. ^ Arnett, Edward B.; Wallace P. Erickson, Jessica Kerns, Jason Horn (June 2005). Relationships between Bats and Wind Turbines in Pennsylvania and West Virginia: An Assessment of Fatality Search Protocols, Patterns of Fatality, and Behavioral Interactions with Wind Turbines (PDF). Bat Conservation International. Retrieved on 2006-04-21. ^ http://www.windpower.org/en/stats/shareofconsumption.htm ^ http://www.windpower.org/composite-1172.htm External links This article or section may contain external links added only to promote a website, product, or service – otherwise known as spam. If you are familiar with the content of the external links, please help by removing promotional links, in accordance with Wikipedia:External links. (you can help!) Technical List of technical books related to wind power/wind turbine design. Global wind power (includes map) Wind Power Impacts on Electric Power System Operating Costs by the U.S. National Renewable Energy Laboratory (2004) Wind Energy Projects and Daily News Average annual wind power map for the U.S. Wind Atlases of the World – The World of Wind Atlases Database of Wind Characteristics - Wind data for wind (turbine) design and wind resource assessment and siting Danish Wind Industry Association Extensive technical information on wind energy. Homebrewed windenergy Discussion of application of wind turbines in cold climates Information about the Annual International Workshop on Large-Scale Integration of Wind Power and Transmission Networks for Offshore Wind Farms Political Asociación Argentina de Energía Eólica - AAEE - Argentine Wind Energy Association, (Argentina) World Wind Energy Association WWEA German Wind Energy Association BWE Spanish Wind Energy Association (Asociación Empresarial Eólica) The British Wind Energy Association American Wind Energy Association African Wind Energy Association -- AfriWEA is a non-profit organisation formed in 2002 to encourage manufacturers, developers, governments, renewable energy owners and individuals to promote and support wind energy development on the African continent European Wind Energy Association Extensive information and myth debunking in the report: windenergy the facts. Canadian Wind Energy Association Alliance to Protect Nantucket Sound Citizens group opposed to plans for USA's first offshore wind facility. Capewind -- Website of USA's first offshore wind facility. Country Guardian -- A UK NGO opposed to the construction of wind turbines. Windustry -- A non-profit organization working to increase wind energy opportunities for rural landowners and communities. National Wind Watch -- A US coalition of citizens and grassroots groups to promote knowledge and raise awareness of the damaging impacts of industrial wind turbine development. Industrial Wind Energy Opposition -- Resources for debunking claims, documenting ill effects, and fighting the spread of industrial wind power Iberica 2000.org - On the serious impact of wind farms on birds. "We Must Increase Our Gust" - On wind power's ability to replace other sources, with lively forum discussion. "Shooting Down the Breeze" - On wind power industry's ambivalent concern about wildlife impacts, also with lively forum discussion. Wind Works --An extensive personal site on windpower. Nuanced pro wind energy. yes2wind -- A website by Greenpeace, Friends of the Earth and the WWF in support of wind energy in support of the wind industry. ExternE -- The European research project about the external costs of energy production in general. Wind systems - On the site of the Australian Greenhouse Office. Windpower Monthly -- Wind Energy Magazine. Enertrag.de -- A German energy company investing in wind turbines. Owns 13 wind parks as of October 2004. POWER - Pushing Offshore Wind Energy Regions -- POWER is an European Interreg project which establishes a discussion platform and a support of European regions in the development of offshore-windenergy projects. Wind power projects Altamont Pass Austin Energy's GreenChoice Program Cape Wind (Massachusetts) Gharo Wind Power Plant in Pakistan Database of projects throughout the United States Denham - Wind Diesel in Western Australia. First Community Based Project in Hull, MA Judith Gap Wind Farm (Montana) now on-line Kite Wind Generator, (Italy) Mawson Station - High Penetration (>90%) Wind Diesel at Mawson Station in Antarctica. Middelgrunden offshore wind farm, (Denmark) Projects planned for Texas Wenerenergi Sweden Windiberica Wind Farm Projects (Spain) Home made small scale wind power generator and battery storage (South Africa) Academic institutions Endowed Chair of Wind Energy – Stuttgart University Wind Energy Department – Risø National Laboratory Wind Energy at Appalachian State University - Boone, North Carolina Other (and unclassified) external links Wikimedia Commons has media related to: Category:Wind power World Wind Energy Association UK's Royal Academy of Engineering report on the cost of electricity generation Wind Power in the UK by the Sustainable Development Commission A new gust of wind projects across the US High natural-gas prices and global-warming concerns may help wind energy gain critical mass. By Mark Clayton, Christian Science Monitor, January 19, 2006 "Wind versus water: Measuring the potential of our renewable resources" from Canadian Geographic Climate Change Chronicles article about offshore wind energy in Europe Wind farms could meet energy needs Instructions to make Wind Power at Home 'Enough wind offshore to electrify America' Cape Cod Today 30 September 2005 theWatt.com Website and podcast about energy and environment The British Library - finding information on the renewable energy industry The Wind Power - wind energy database Pictures, technical data, links... WWW-VL Wind Power In Kansas Wind power in the news Energy and Environment - Wind at the Open Directory Project Energy Conversion   Edit Active solar | Anaerobic digestion | Barra system | Biomass | Blue energy | Deep lake water cooling | Distributed generation | Earth cooling tubes | Electricity generation | Energy Tower | Fuel cell | Fusion power | Geothermal power | Hydroelectricity | Hydrogen production | Mechanical biological treatment | Microgeneration | Ocean thermal energy conversion | Passive solar | Photovoltaics | Seasonal thermal store | Solar cell | Solar panel | Solar pond | Solar power | Solar power tower | Solar thermal energy | Solar tracker | Solar updraft tower | Sustainable community energy system | Tidal power | Trombe wall | Water turbine | Wave power | Wind farm | Wind power | Wind turbine Sustainability and Development of Energy   Edit Conversion | Development and Use | Sustainable Energy | Conservation | Transportation Search Term: "Wind_power" Categories: Articles with unsourced statements | Wikipedia spam cleanup | Alternative energy | Power stations | Energy conversion | Industries | Production | Renewable energy | Sustainable technologies | Turbines | Wind farms

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