A wind turbine is a machine that changes the movement energy of wind into electricity. In 2024, hundreds of thousands of large wind turbines, grouped in areas called wind farms, produced over 1,136 gigawatts of power. Each year, an additional 117 gigawatts of power were added. Wind turbines are becoming an important source of renewable energy that is not always available. They are used in many countries to help reduce energy costs and dependence on fossil fuels. A study from 2009 found that wind energy had the lowest greenhouse gas emissions, used the least water, and had the most positive effects on society compared to solar, hydro, geothermal, coal, and gas energy sources.

Wind turbines come in many sizes and designs. Most have horizontal axes, with three blades positioned in front of their towers. Some have vertical axes and include different designs, such as the "eggbeater" Darrieus, the giromill with straight blades, the Savonius with curved blades for rooftops and ships, airborne models with wings attached to the ground, floating models on platforms, and other unique designs like those with counter-rotating blades.

The blades of wind turbines are often made from glass fiber composites. Carbon fiber, which is stronger and lighter, is also used in some cases. Smaller turbines are used for tasks like charging batteries or powering remote devices, such as traffic signs. Larger turbines can provide electricity for homes and sell extra power to the electrical grid.

Wind energy is one of the cheapest renewable energy sources and does not produce greenhouse gases. However, wind turbines can affect wildlife, though these effects can be reduced. Wind energy production depends on wind speed, not on how much electricity is needed, so it is not always reliable unless energy storage systems are available.

History

The windwheel created by Hero of Alexandria (10–70 CE) is one of the earliest known examples of wind power being used to operate a machine. The first practical wind power plants were built in Sistan, an Eastern province of Persia (now Iran), during the 7th century. These windmills, called panemone windmills, had vertical drive shafts with rectangular blades. Each windmill had six to twelve sails made of reed matting or cloth. They were used to grind grain or pump water and were important in industries like milling and sugarcane processing.

Wind power was first used in Europe during the Middle Ages. Historical records in England show windmills were used as early as the 11th and 12th centuries. German crusaders brought windmill-making skills to Syria around 1190. By the 15th century, Dutch windpumps were used to drain wetlands. Vertical-axis wind turbines were described by Croatian inventor Fausto Veranzio in his book Machinae Novae (1595).

The first electricity-generating wind turbine was installed by Austrian inventor Josef Friedländer at the Vienna International Electrical Exhibition in 1883. It was a Halladay wind turbine used to power a dynamo. Friedländer’s wind turbine had a 6.6-meter (22-foot) diameter and was made by the U.S. Wind Engine & Pump Co. of Batavia, Illinois. It produced 3.7 kilowatts (5 horsepower) of electricity, which powered tools, lamps, and a threshing machine. The turbine and its parts were displayed at the main exhibition hall in Vienna’s Prater.

In July 1887, Scottish academic James Blyth built a wind-powered machine to light his home in Marykirk, Scotland. Later that year, American inventor Charles F. Brush created the first automatically operated wind turbine after working with professors and colleagues. His design was reviewed by experts for electricity production. Although Blyth’s turbine was not cost-effective in the UK, wind power was more economical in countries with widely spread populations.

By 1900, Denmark had about 2,500 windmills used for tasks like pumping water and grinding grain, producing up to 30 megawatts of power. The largest windmills stood on 24-meter (79-foot) towers with four-bladed 23-meter (75-foot) rotors. By 1908, 72 wind-driven electric generators operated in the United States, ranging from 5 to 25 kilowatts. Around World War I, American manufacturers produced 100,000 wind turbines yearly, mostly for water pumping.

By the 1930s, wind turbines in rural areas were less commonly used as electrical systems expanded to those regions. A predecessor of modern horizontal-axis wind generators was installed in Yalta, USSR, in 1931. It was a 100-kilowatt generator on a 30-meter (98-foot) tower with an annual capacity factor of 32 percent, similar to modern wind machines.

In 1941, the first megawatt-class wind turbine was connected to a power grid in Vermont. The Smith–Putnam wind turbine operated for about five years before a blade broke. It was not repaired due to material shortages during the war. The first utility grid-connected wind turbine in the UK was built by John Brown & Company in 1951 in the Orkney Islands.

In the early 1970s, anti-nuclear protests in Denmark led to the development of small 22-kilowatt wind turbines. Organizing groups of turbine owners helped push for government support and incentives for larger turbines in the 1980s. Activists in Germany, early turbine makers in Spain, and investors in the U.S. in the 1990s also promoted policies to grow the wind power industry.

Some experts argue that expanding wind power may increase competition over rare materials like neodymium, praseodymium, and dysprosium. However, this view has been criticized for not recognizing that most wind turbines do not use permanent magnets and for ignoring economic incentives to produce these materials.

• Nashtifan wind turbines in Sistan, Iran
• A vertical-axis wind turbine design by Fausto Veranzio, around 1600
• Wind turbine for power generation by Josef Friedländer, Vienna in 1883
• James Blyth’s electricity-generating wind turbine, 1891
• The first automatic wind turbine, built in Cleveland in 1887 by Charles F. Brush

Wind power density

Wind power density (WPD) is a way to measure how much wind energy is available in a place. It shows the average power that can be captured by the area covered by a turbine's blades. WPD is calculated for different heights above the ground and takes into account wind speed and air density.

Wind turbines are grouped into classes I, II, and III based on the wind speed they are built for. These classes also use letters A, B, and C to describe how rough or turbulent the wind is in that area.

Efficiency

The law of conservation of mass states that the amount of air entering a turbine must equal the amount of air leaving it. Similarly, the law of conservation of energy requires that the energy from the wind entering the turbine equals the sum of the energy in the wind leaving the turbine and the energy converted to electricity. Since wind leaving the turbine still has some kinetic energy, only a limited amount of the incoming energy can be used to produce electricity. Betz's law explains this limit, called Betz's coefficient, which is 16⁄27 (about 59.3%) of the energy from the wind arriving at the turbine.

The maximum power a wind turbine can produce is 16⁄27 of the energy from the wind passing through the area of the turbine’s blades. If the area of the turbine’s blades is A and the wind speed is v, the maximum power P can be calculated using the air’s density (ρ).

Efficiency is affected by factors such as friction and drag on the turbine blades. Additional losses occur in parts like the gearbox and generator, reducing the electricity produced. To protect the turbine, power is kept constant when wind speed exceeds the turbine’s rated speed, even though theoretical power increases with the cube of wind speed. In 2001, wind turbines connected to the power grid achieved 75% to 80% of Betz’s limit at rated wind speeds.

Over time, efficiency may decrease due to factors like dust and insect remains on blades, which change the blade shape and reduce performance. A study of 3,128 wind turbines in Denmark found that half showed no efficiency loss, while the other half lost about 1.2% of their power output each year.

Stable weather conditions, such as steady wind speeds, improve turbine efficiency by about 15% compared to unstable conditions. This is because stable air allows wind to recover more quickly after passing through the turbine. However, unstable air can also lead to faster recovery of wind flow in some cases.

The materials used for turbine blades affect efficiency. In an experiment, blades made of heavier materials, like glass and carbon epoxy, created more friction and lower power output compared to lighter materials.

Wind speed is the most important factor affecting turbine efficiency. This is why choosing the right location is critical. Wind tends to be stronger near coasts due to temperature differences between land and water. Placing turbines on mountain ridges also increases wind speed, as higher altitudes generally have faster winds. Windbreaks can further increase wind speed near turbines.

Types

Wind turbines can rotate around a horizontal or vertical axis. Horizontal-axis turbines are older and more common. They may have blades or be bladeless. Small vertical-axis turbines used at homes make less power and are less common.

Most wind power today comes from large horizontal-axis wind turbines (HAWTs) with three blades. These blades face the wind, and the main parts of the turbine are at the top of a tower. These turbines must face the wind directly. Small turbines use a simple wind vane to turn, while large ones use a wind sensor and a system called a yaw system. Many turbines have a gearbox, which speeds up the slow rotation of the blades to power a generator. Some turbines use direct-drive generators that connect the rotor directly to the generator without a gearbox. These direct-drive systems are more expensive but avoid problems with gearboxes, such as wear and maintenance costs. Some turbines use a different type of direct-drive system that has advantages over others.

Most horizontal-axis turbines have their blades facing the wind before the tower. Some turbines have blades that face away from the wind, which avoids needing extra parts to keep them aligned. In strong winds, these blades can bend to reduce wind resistance. However, upwind designs are preferred because the wind changes as blades pass the tower, which can damage the turbine.

Wind turbines used for power production usually have three blades. These blades are white for visibility to planes and range from 20 to 80 meters long. Turbines are getting larger each year. Offshore turbines can be as large as 26 megawatts with blades up to 153 meters long. Onshore turbines can reach up to 15 megawatts with blades up to 131 meters long. The average height of onshore turbines in the U.S. is 103 meters, while global offshore turbines average 124 meters.

• Parts of a horizontal-axis turbine, such as the gearbox and rotor, being placed in position.
• A gearless turbine’s rotor being set up. This turbine was built in Germany and later moved to the U.S.
• Offshore horizontal-axis turbines at Scroby Sands Wind Farm in England.
• Onshore horizontal-axis turbines in Zhangjiakou, Hebei, China.

Vertical-axis wind turbines (VAWTs) have their main shaft arranged vertically. A benefit is that they do not need to face the wind directly, which is helpful in areas with changing wind directions. This design is also useful for buildings because it is less steerable. The generator and gearbox can be placed near the ground, making maintenance easier. However, vertical-axis turbines produce less energy over time compared to horizontal-axis turbines.

Vertical-axis turbines are less efficient than horizontal-axis turbines. Problems include slower rotation, higher torque costs, lower power output, and challenges in predicting wind flow. These issues make them harder to design and maintain.

When a turbine is placed on a rooftop, the building can increase wind speed at the turbine. The best height for a rooftop turbine is about half the building’s height to get the most wind energy with less turbulence. While wind speeds in cities are lower than in open areas, noise and building strength are important factors.

Vertical-axis turbines include types like the Darrieus turbine, named after a man who patented it in the 1920s. These turbines have good efficiency but cause uneven torque, which can damage the tower. Using three or more blades reduces this issue. The giromill is a Darrieus turbine with straight blades. The cycloturbine has adjustable blades to reduce torque changes and starts on its own.

Savonius turbines use curved blades and are used in devices like anemometers and vents on vehicles. They start on their own with at least three blades. A modified version called the twisted Savonius has smooth blades and is used on rooftops and ships. Airborne turbines use wings or small aircraft attached to the ground to reach high winds. Prototypes are used in East Africa. Floating turbines are offshore turbines on platforms that float, allowing them to be placed in deeper water and reducing visual concerns.

• Counter-rotating wind turbine
• Vertical-axis wind turbine offshore
• Light pole wind turbine

Design and construction

Wind turbines change wind energy into electrical energy that can be used. Traditional wind turbines with horizontal blades have three main parts:

• The rotor, which costs about 20% of the turbine’s total price, includes the blades that turn wind energy into slow rotational movement.
• The generator, which costs about 34% of the turbine’s total price, includes the electrical generator, control systems, and parts like a gearbox, adjustable-speed drive, or continuously variable transmission. These parts change slow rotation into fast rotation needed to create electricity.
• The surrounding structure, which costs about 15% of the turbine’s total price, includes the tower and the mechanism that allows the rotor to turn toward the wind.

A common 1.5-megawatt wind turbine in the United States has a tower 80 meters (260 feet) tall. The rotor (blades and hub) is about 80 meters (260 feet) wide. The nacelle, which holds the generator, is 15.24 meters (50 feet) long and weighs about 300 tons.

Because of problems with sending data, monitoring the health of wind turbines often uses several accelerometers and strain gages attached to the nacelle to check the gearbox and other equipment. Today, digital image correlation and stereophotogrammetry are used to measure how wind turbine blades move. These methods usually track movement and strain to find where damage might occur. The movement patterns of non-rotating wind turbines have been studied using digital image correlation and photogrammetry. Three-dimensional point tracking has also been used to measure the movement of rotating wind turbine parts.

Technology

Generally, turbine blade efficiency improves as blade lengths increase. Blades must be stiff, strong, durable, lightweight, and resistant to wear. Materials with these qualities include composites like polyester and epoxy, with glass fiber and carbon fiber used for reinforcement. Manufacturing methods may include manual layering or injection molding. Upgrading existing turbines with longer blades can reduce the need for redesigning entire systems.

Wind turbines typically last about 30 years, but blades and gearboxes often need replacement after 25 years.

Common materials used in wind turbine blades are described below.

The stiffness of composites depends on the stiffness of the fibers and how much of the material they make up. E-glass fibers are often used as the main reinforcement in composites. Glass/epoxy composites for wind turbine blades usually contain up to 75% glass by weight. This increases stiffness, tensile strength, and compression strength. A promising material is glass fiber with modified versions like S-glass or R-glass. Other types of glass fiber developed by Owens Corning include ECRGLAS, Advantex, and WindStrand.

Carbon fiber has greater tensile strength, higher stiffness, and lower density than glass fiber. A part of the blade called the spar cap, which experiences high tension, benefits from carbon fiber. A 100-meter (330 ft) glass fiber blade could weigh up to 50 tonnes (110,000 lb), but using carbon fiber in the spar can save 20% to 30% of the weight, about 15 tonnes (33,000 lb).

Instead of using only glass or only carbon fiber for reinforcement, hybrid designs balance weight and cost. For example, replacing 80% of a blade’s material with carbon fiber could save 80% of the weight but increase costs by 150%. Replacing 30% of the material with carbon fiber would save 50% of the weight and increase costs by 90%. Hybrid materials include combinations like E-glass and carbon fiber or E-glass and aramid fiber. The longest blade made by LM Wind Power uses a hybrid of carbon and glass fiber. More research is needed to find the best material mix.

Adding small amounts (0.5% by weight) of nanomaterials like carbon nanotubes or nanoclay to composites can improve strength, durability, and resistance to breaking by 30% to 80%. Studies show that adding small amounts of carbon nanotubes can extend the lifespan of materials up to 1,500 times.

In 2010, the average cost of a wind turbine was about $2,324 per kilowatt. By 2024, this cost had dropped to $1,041 per kilowatt, decreasing by about 12% each year. Home wind turbines are cheaper, with small 400 W turbines costing as little as $700 in the U.S. (not including installation).

The average cost of energy from wind turbines, called the levelized cost of energy (LCOE), ranged from $25 per megawatt-hour (MWh) in China to $70 per MWh in Vietnam in 2025. Globally, the average was about $50–60 per MWh. The Middle East and North Africa region had the lowest average LCOE, with a project in Saudi Arabia achieving $15.66 per MWh in 2024.

For turbine blades, hybrid glass/carbon fiber blades cost more in materials than all-glass blades, but labor costs may be lower. Carbon fiber allows simpler designs that use less material. The main process in blade manufacturing is layering plies. Thinner blades require fewer layers, reducing labor costs in some cases.

Offshore wind turbines have higher installation costs. In 2024, the average total installation cost for offshore turbines was $2,852 per kilowatt, down 48% from 2010 costs of $5,518 per kilowatt.

Parts of wind turbines other than the blades (like the hub, gearbox, frame, and tower) are mostly made of steel. Smaller turbines and some large Enercon turbines use aluminum alloys to reduce weight and improve efficiency. This trend may grow if the strength and fatigue resistance of aluminum improve. Pre-stressed concrete is increasingly used for towers but still needs a lot of steel reinforcement. Step-up gearboxes are being replaced with variable speed generators, which require magnetic materials.

Modern turbines use about two tons of copper for wiring, generators, transformers, and grounding systems because of copper’s excellent electrical conductivity and durability. In 2018, global wind turbine production used 450,000 tonnes of copper per year. By 2025, copper use ranged between 650 and 6,200 kg per megawatt of power generated.

A 2015 study on wind energy in Europe found that larger turbines use more precious metals but require less material per kilowatt of power generated. Material use in the European Union doubled between 2009 and 2020. For example, the

Wind turbines on public display

Some areas have used the eye-catching nature of wind turbines by displaying them in public spaces, such as by building visitor centers near their bases or creating viewing areas farther away. These wind turbines are typically standard horizontal-axis designs with three blades and produce electricity for power grids. However, they also have unusual purposes, such as showing how technology works, helping with public communication, and teaching people about energy. The Bahrain World Trade Center has wind turbines that are clearly visible to the public. It is the first skyscraper to include wind turbines as part of its structure.

Small wind turbines

Small wind turbines can be used for many purposes, such as homes connected to or not connected to the power grid, communication towers, offshore structures, schools and clinics in rural areas, and remote monitoring systems. These turbines can be as small as a 50-watt generator, which is used on boats or caravans. Systems that combine solar and wind energy are becoming more common for traffic signs, especially in rural areas, because they reduce the need for long power lines to connect to the main electricity supply. According to the U.S. Department of Energy's National Renewable Energy Laboratory (NREL), small wind turbines are those with a capacity of 100 kilowatts or less. These smaller turbines often use direct-drive generators, produce direct current electricity, have blades that adjust to wind movement, and include bearings designed to last a long time. They also use a vane to face the direction of the wind.

Wind turbine spacing

In most wind farms with horizontal wind turbines, the distance between turbines is usually about 6 to 10 times the width of the turbine's spinning part, called the rotor. However, for very large wind farms, placing turbines about 15 rotor widths apart may be more cost-effective, considering the size of the turbines and the cost of land. This finding comes from research by Charles Meneveau of Johns Hopkins University and Johan Meyers of Leuven University in Belgium. Their study used computer models to analyze how wind turbines interact with each other and with the wind in the atmosphere.

Research by John Dabiri of Caltech shows that vertical wind turbines can be placed closer together if they follow an alternating pattern of rotation. This pattern allows the blades of nearby turbines to move in the same direction as they approach each other.

Operability

Wind turbines require regular maintenance to remain reliable and operational. Ideally, turbines can generate energy 98% of the time. Ice build-up on turbine blades significantly reduces their efficiency, which is a common problem in cold climates where icing and freezing rain occur. Deicing is usually done using internal heating or, in some cases, by helicopters or drones that spray warm water onto the blades.

Modern turbines often include a small onboard crane to lift tools and replace minor parts. However, large and heavy components like generators, gearboxes, and blades are rarely replaced. In such cases, a heavy lift external crane is needed. If the turbine is in an area with difficult access, a containerized crane can be lifted by the internal crane to handle heavier tasks.

Installing new wind turbines can sometimes cause controversy. An alternative is repowering, which involves replacing older turbines with larger, more powerful ones. This process may use fewer turbines while maintaining or increasing energy production.

Some retired wind turbines are recycled or repowered. About 85% of turbine materials can be reused or recycled. However, turbine blades, made of composite materials, are harder to process.

Recycling blades depends on local laws and economic factors. A challenge is the composite material used, which includes fiberglass and carbon fibers in epoxy resin. This material cannot be remolded into new composites.

Wind farm waste is less harmful than other types of waste. Wind turbine blades make up only a small part of total waste in the United States, according to the American Wind Energy Association.

Several companies, researchers, and utilities are working on ways to reuse or recycle blades. For example, Vestas has developed a method to separate fibers from resin for reuse. In Germany, blades are recycled as part of fuel for a cement factory. In the United Kingdom, a project is testing the use of blade strips as rebar in concrete for a high-speed rail project. In Poland and Ireland, used blades have been incorporated into pedestrian bridge supports. In 2026, a Chinese company, Ming Yang, created the first fully recyclable turbine using pultruded carbon fiber panels. This design allows components to be separated through a chemical process.

Comparison with other power sources

Wind turbines are one of the least expensive sources of renewable energy, along with solar panels. As technology for wind turbines has improved over time, their costs have decreased. Wind energy currently does not have a competitive market because wind is a free natural resource that is mostly not used. The main cost of small wind turbines is the price to buy and install them, which averages between $48,000 and $65,000 per installation. Usually, the amount of energy produced by wind turbines is greater than the cost of the turbines.

Wind turbines provide clean energy. They use little water and do not produce harmful gases or waste during operation. Using a one-megawatt wind turbine instead of one megawatt of energy from fossil fuels can reduce carbon dioxide emissions by over 1,400 tonnes (1,500 short tons) each year.

Wind power can affect wildlife, but these effects can be reduced with proper planning. Thousands of birds, including some rare species, have been killed by wind turbine blades. However, wind turbines cause very few bird deaths compared to other human activities. Wind farms and nuclear power plants cause about 0.3 to 0.4 bird deaths per gigawatt-hour (GWh) of electricity, while fossil fuel power plants cause about 5.2 bird deaths per GWh. Coal-fired power plants contribute much more to bird deaths. A study of bird populations in the United States from 2000 to 2020 found that wind turbines did not significantly affect bird numbers.

Energy from wind turbines changes depending on wind conditions and is not always available when electricity is needed. Turbines are often placed on ridges or bluffs to capture more wind, but this limits where they can be built. Because of this, wind energy is not always reliable. However, wind energy can be part of a mix of energy sources, including other types of power. Scientists are working on ways to store extra energy, which can help when wind energy is not available.

Wind turbines have blinking lights to warn airplanes and avoid collisions. Some people who live near wind farms, especially in rural areas, say these lights cause light pollution. A solution is to use Aircraft Detection Lighting Systems (ADLSs), which turn the lights on only when the system’s radar detects planes within certain distances and heights.