Wind energy FAQs


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Wind power FAQs

How can the wind be measured?

Wind is usually measured by its speed and direction. Wind atlases show the distribution of wind speeds on a broad scale, giving a graphical representation of mean wind speed (for a specified height) across an area. They are compiled by local meteorological station measurements or other wind-related recorded data.

Traditionally, wind speed is measured by anemometers - usually three cups that capture the wind rotating around a vertical axis (pictured below). The wind direction is measured with weather vanes.

After measuring wind data for at least one year, the mean annual wind speed can be calculated. Wind speed and wind direction statistics are visualised in a wind rose, showing the statistical repartition of wind speed per direction.

Wind statistics show the best sites to locate wind farms according to the best wind resources. They also provide further information on how the turbines should be positioned in relation to each other and what the distance between the turbines should be.

How big is a wind turbine?

The average size of onshore turbines being manufactured today is around 2.5-3 MW. It can power more than 1,500 average EU households.

The largest offshore turbine is a 8 MW turbine with a rotor diameter of 164 m.

How does a wind turbine produce electricity?

The wind passes over the blades creating lift (like an aircraft wing) which causes the rotor to turn. The blades turn a low-speed shaft inside the nacelle. From there, there are two major variations:

a) the shaft is connected to a gearbox which raises the low speed of the rotor shaft to a high speed shaft that drives a generator. Here, the slow rotation speed of the blades is increased to the high speed of generator revolution - usually 1500rpm in Europe and most of Asia to produce 50hz; or 1800 rpm in North America to produce 50hz

b) in 'direct drive' turbines' the rotor shaft is connected directly to the generator, which is generally much larger and more electrically complex.

Electricity from the generator goes to a transformer which converts it to the right voltage for the electricity grid. The electricity is then transmitted via the electricity network.

What is a wind turbine made of?

The towers are mostly tubular and made of steel or concrete, generally painted light grey. The blades are made of fibreglass, reinforced polyester or wood-epoxy. They are light grey because it is inconspicuous under most lighting conditions. The finish is matt, to reduce reflected light.

How fast do the blades turn?

The blades rotate between 15-20 revolutions per minute at constant speed. However, an increasing number of machines operate at variable speed, where the rotor speed increases and decreases according to the wind speed.

How much electricity can one wind turbine generate?

The output of a wind turbine depends on the turbine's size and the wind's speed through the rotor. Wind turbines manufactured today have power ratings ranging from 250 watts to 7 MW. An onshore wind turbine with a capacity of 2.5 MW can produce more than 6 million kWh in a year - enough to supply 1,500 average EU households with electricity.

What happens when the wind stops blowing?

The power system operator constantly matches the electricity generation available to electricity demand. No power plant is 100 per cent reliable, and wind power is variable but predictable, allowing hours or even days for system operators to compensate for changing wind conditions. Wind farm sites are chosen after careful analysis of wind patterns. This information is made available to the network operators who will distribute the electricity.

The power grid is designed to cope with power plants shutting down unexpectedly; wind energy is often referred to as 'intermittent', but 'variable' is a much better word. What is 'intermittent' is a nuclear power plant which can (and often does) go from 1,000 MW of production to zero in less than one second; that will never happen with wind power.

Why do some of the turbines in a wind farm sometimes stand still?

Turbines sometimes have to be stopped for maintenance, for repairing components or if there is a failure that needs to be checked. Another reason can be too little or too much wind: if the wind is too strong, the turbine needs to be shut down because it could be damaged.

How long does a wind turbine work for?

The 'design' life of a wind turbine is usually 20 years. Wind power is a relatively new industry, however, so there are actually very few machines that have reached that age yet. Some turbines in Germany and Denmark have been spinning quite happily well past their 20 year design life while others have been replaced before the end of their design life because the technology has evolved so rapidly.

How is a wind farm designed?

There are many factors at play when designing a wind farm. Ideally, the area should be as wide and open as possible in the prevailing wind direction, with few obstacles. Its visual influence needs to be considered: few, larger turbines are usually better than many smaller ones.

The turbines need to be easily accessible for maintenance and repair work when needed. Noise levels can be calculated so the farm is compatible with the levels of sound stipulated in national legislation. The turbine supplier defines the minimum turbine spacing, taking into account the effect one turbine can have on others nearby - the 'wake effect'.

Then, the right type of turbine must be chosen. This depends on the wind conditions and landscape features of the location, local/national rules such as on turbine height, noise levels and nature conservation, the risk of extreme events such as earthquakes, how easy it is to transport the turbines to the site and the local availability of cranes.

How long does it take to build a wind farm?

The actual construction time is usually very short - a 10 MW wind farm can easily be built in two months and a larger 50 MW wind farm can be built in six months.

What are the costs of building a wind farm?

Costs vary but the major cost is the turbine itself. This is a capital cost that has to be paid up front and typically accounts for 75% of the costs. Once it is up and running there are few costs – and of course no fuel and carbon costs.

The total cost per KW of installed wind power worldwide varies from 750 euros to more than 2,000 in high cost countries, such as Japan.

Can wind deliver enough electricity?

Electricity demand is always going up and down - the grid operator's job is to constantly match the electricity generation available to electricity demand. Wind energy's variability is just one more variable in the mix.

Today, in Denmark, about 39% of electricity demand is already supplied by the wind, and is managed successfully by the Transmission System Operator. The Danish government aims to get 50% of its electricity from wind by 2020 and 100% of renewables by 2035. In South Australia 20% of electricity demand is met by wind, and in Iowa, US, 28.5% of electricity was supplied by wind in 2014.

According to GWEC projections (Global Wind Energy Outlook 2014) wind energy will supply between 8% and 12% of the world's electricity by 2020.

In a recent report, the International Energy Agency (IEA) points out that so-called 'variable' energy sources such as wind can be managed with an intelligent, joined-up grid and a functioning electricity market.

Is wind power good for the economy?

Yes! The 44.79 GW of new wind power worldwide, which came online in 2012, represents investments of about $78.3 billion (Bloomberg New Energy Finance 2012). Additionally, approximately 670,000 people were employed directly or indirectly in the global wind power industry. This is expected to grow to 1,214,000 by 2020 and to 2.6 million by 2030 according to the projections in the Global Wind Energy Outlook 2012.

Wind energy makes people less dependent on fuel imports at unpredictable prices. In 2011, wind power production worldwide avoided fuel costs of €35 bn. GWEC estimates this number to grow almost eight times by 2020.

Wind-generated power comes at a zero fuel cost and zero CO2 cost, unlike most traditional energy sources. Wind power can also lower electricity prices and bring more competition to the market.

What other environmental benefits does wind power bring?

Wind energy emits no toxic substances such as mercury and air pollutants like smog-creating nitrogen oxides, acid rain-forming sulphur dioxide and particulate deposits. These pollutants can trigger cancer, heart disease, asthma and other respiratory diseases, can acidify terrestrial and aquatic ecosystems, and corrode buildings.

Wind energy creates no waste or water pollution. Given the fact that water scarcity is pressing and will be exacerbated by climate change and population growth, wind energy is key to preserving water resources. Unlike fossil fuel and nuclear power plants, wind energy has one of the lowest water consumption footprints. This is evident in two of the largest wind power markets, USA and China.

In the USA, under the 20 percent Wind Scenario wind power would reduce the annual water consumption in the electric sector by 17 percent by 2030.

In China, the government aims to increase wind power generation capacity to 200 GW by 2020. If achieved, this could save 800 million cubic meters (m3) of water - equivalent to meeting the water demand of 11.2 million households.

How much CO2 emissions can wind avoid?

The greatest benefit of wind power is its contribution to reduction of carbon dioxide emissions from the power sector, which is the single largest anthropogenic contributor to the global climate change problem.

In 2015 annual reductions in CO2 from existing wind power plant is about 500 million tonnes. Under the Global Wind Energy Outlook moderate scenario, this is expected to rise to 1.1 billion tonnes annually by 2020 and up to 2.5 billion tonnes per year by 2030.

What are the top wind power countries in the world?

Wind energy is now present in more than 80 countries, with 24 countries having more than 1,000 megawatts installed. The top five markets in the world in 2014 were China, Germany, USA, Brazil and India.

In cumulative terms the top five markets are China, USA, Germany, Spain and India.

See more details in GWEC graphs and figures at

How many people are employed by the wind industry globally?

Did you know that a wind turbine consists of more than 8,000 parts? Then consider how many jobs are created in the supply chain from ball bearings to fiberglass housing.

In 2012, approximately 670,000 people were employed directly or indirectly in the global wind power industry. According to Global Wind Energy Outlook 2012 moderate scenario, wind energy could generate over 2.6 million jobs globally by 2030.

In Brazil alone, 15,000 new jobs were created by the wind industry in 2012.

Jobs range from manufacturing to services and development. There is currently a shortage of skilled workers and engineers in the wind business.

How popular are wind farms?

Opinion polls and surveys across the markets worldwide show overwhelming public support for wind power providing an important signal to decision-makers: According to a Eurobarometer survey 89% of EU citizens are in favour of wind energy, compared to 43% for coal and 36% for nuclear. In 2012 a survey conducted in the US showed that 71% of Americans want to see more wind power development and in Canada a research poll found that 78% of Ontarians say that wind is one of the safest forms of electricity generation. In a recent survey in the UK, two-thirds of the Britons voted in favour of wind energy.

Awareness campaigns such as the Global Wind Day help inform Europeans and people around the world about the benefits of wind energy.

Does the wind industry depend on government subsidies?

While many governments support electricity produced by wind, oil, gas, coal and nuclear all receive subsidies, and, despite having been subsidised for more than 50 years, continue to get substantially more than wind. According to the International Energy Agency fossil fuels are today receiving seven times the level of subsidies of renewable energy. The level of subsidies to fossil fuels has gone up by nearly 30% to $620 billion since 2010 and today fossil fuels receive six times more subsidies than renewable energy. Meanwhile atmospheric global carbon dioxide levels have reached a record high of 400 ppm seriously hindering efforts to bring human-produced emissions under control. Fossil fuel energy subsidy reform could take us a long way towards protecting the climate.

How many wind turbines are there in the world?

At the end of 2014 there were more than 268,000 wind turbines operating around the world in about 80 countries. As technology progresses, turbines are becoming bigger and more efficient. The same amount of energy can be generated with fewer machines.

Do wind turbines affect human health?

Wind energy is one of the cleanest, most environmentally-friendly energy sources. It emits no greenhouse gases or air pollutants. It emits no particles of any kind, and certainly no particles which are carcinogenic and severely affect human health, as do fossil fuels.

Despite some claims to the contrary, an increasing quantity of independent research indicates that wind turbines are not harmful to human health. The wind industry is committed to engagement with experts in science, medicine and occupational and environmental health to monitor on-going credible research in the area of wind turbines and human health.

A study, Wind Turbine Sound and Health Effects, was conducted in 2009 by a panel of medical professionals from the US, Canada, Denmark, and UK. The study concluded, "There is no evidence that the audible or sub-audible sounds [including infrasound] emitted by wind turbines have any direct adverse physiological effects."

The Australian government and the National Health and Medical Research Council (NHMRC) conducted a study on "Wind Turbines and Health" (2010) which concluded: "There are no direct pathological effects from wind farms; any potential impact on humans can be minimised by following existing planning guidelines".

In July 2012, Health Canada published the results of a national study on wind turbines, sound and human health; and concluded that wind energy is one of the safest sources of electricity. See a summary of the main conclusions reached in 17 reviews of the research literature on wind farms and health:

The 17 reviews of the research literature on wind farms and health can be viewed here.

How much electricity is created from wind worldwide?

Wind power currently supplies about 2.5 percent of global electricity consumption. Industry projections show that wind power will, with the right policy support, double in capacity by 2015 and again by the end of this decade. This will deliver somewhere between 8 and 12 percent of global electricity supply. Wind provides 30% of electricity in Denmark and also makes a double digit contribution of 16% in  Portugal and Spain. It contributes more than 40% of annual electricity in three German states and 20% of South Australia's electricity.