Wind energy is the process by which the wind is used to generate mechanical power or electricity. People have been using energy from the wind for hundreds of years to pump water or grind grain. Today, we use a wind turbines to generate electricity. Wind power has a relatively high output, but only a fraction of its potential is currently used. Wind power plants cannot produce power on demand—their output depends on how hard the wind blows. So, wind power is often used as a supplement to other power sources. Wind power plants are also not feasible for all geographical locations. For example, very cold areas may not be ideal for wind power because of a small chance for ice being thrown off the turbine blades.
Wind is a form of solar energy. The sun’s radiation heats different parts of the Earth at different rates—most notably during the day and night—influenced by the shape of the planet’s terrain, bodies of water, and vegetation. Hot air rises, reducing the atmospheric pressure at the Earth’s surface, and cooler air is drawn in to replace it. The result is wind.
Wind energy does not produce harmful greenhouse gases or waste products. According to the American Wind Energy Association, wind reduces emissions. One modern turbine could prevent 1,500 tons of carbon dioxide from being released into the atmosphere in the US each year.
Wind turbines may pose a threat to birds and bats. Areas that are home to endangered species should not be considered suitable for the development of wind power plants. But overall, wind turbines pose a far smaller threat to birds and bats than buildings, cars and predatory animals (for example, house cats are believed to kill 1 billion birds every year in the US alone!).
How Wind Energy is Formed and Used
Wind turbines convert kinetic energy in the wind into mechanical power. This mechanical power can be used for specific tasks (such as grinding grain or pumping water) or a generator can convert this mechanical power into electricity. A typical horizontal wind machine is as tall as a 20-story building. Wind machines need to be very tall to capture enough wind to generate large amounts of electricity. An average wind speed of only 14 miles (22.5 kilometers) per hour is needed to convert wind energy into electricity.
Wind power plants create little disruption to local ecosystems. Utility-scale wind power plants built on open terrain require about 60 acres per megawatt of installed capacity. But, according to the American Wind Energy Association, only about 5% of this area is needed for the actual turbines and other equipment. The rest of the land can be used for other purposes like farming and ranching.
Wind energy is gaining popularity around the world. Scotland, for example, is home to the United Kingdom’s largest wind farm, in addition to two huge offshore wind turbines and several other onshore wind farms. Scotland’s windy climate makes it the perfect spot for successful wind turbines. Scotland’s government wants to generate 31% of its electricity from renewable energy by 2011, with much of that coming from wind power.
And in China, which has a vast amount of land and a long coastline, wind power has great potential to generate power for the country’s large population. Around 80 wind farms are currently operating in China, and more than a dozen Chinese companies are building wind turbines and their accompanying components. But the country is experiencing some problems with wind power, because not all of its current wind power capacity is connected to its power grids, meaning some wind power (about 28%, according to China Power Union) is lost.
Wind power has a high initial cost – building the turbines, towers and foundations is expensive.
However, wind energy is becoming more affordable as technology improves. According to RenewableUK, world wind energy capacity doubled every three years between 1990 and 2002, and with each doubling, prices fell by 15%.
Some critics of wind energy say that wind turbines are unsightly. Industry professionals work to minimize this issue by using computer simulations to evaluate the visual impact before construction beings and by using turbines that are the same size and spacing them out evenly once the project is approved.
Are Wind Turbines Noisy?
A common concern about wind power plants is noise: Don’t those huge turbines make a lot of noise when they’re spinning? While turbines do make noise, it is generally not loud enough to be disruptive to people’s day-to-day activities. Earlier turbine models were much noisier than today’s models, which have been redesigned to be more streamlined and efficient (and considerably quieter!). According to a study by a panel of doctors, audiologists and acoustical professionals from the US, Canada, Denmark and the United Kingdom, the sounds generated by wind turbines are not harmful to human health. The study, commissioned by the American Wind Energy Association and the Canadian Wind Energy Association, found that the noise generated by wind turbines is no worse than the noise generated in average urban environments. The mechanical components of wind turbines do, of course, make some noise. But since the nearest houses are usually at least 300 meters/984 feet away, RenewableUK asserts that the noise that can be heard inside the houses would be comparable to that inside a quiet, air-conditioned office.
People who live near the turbines may argue this point, though. For example, in Minnesota (in northeastern US), where people may live within 152 meters/500 feet of turbines in rural areas, critics say the noise is a constant hum that disrupts their lives. New York doctor Nina Pierpoint, who has studied the effects of turbines on people, developed the term “wind turbine syndrome,” the symptoms of which are ear pressure, sleep disturbance, vertigo, nausea, blurred vision, memory problems and panic attacks. Critics in Minnesota want regulations to mandate greater distances between turbines and homes (from Noise, Shadows From Wind Farms are Creating Uproar in Rural Minnesota, by Tom Meersman, Minneapolis Star Tribune, 17 Jan., 2010).
Shadow Flicker
Wind turbines’ turning blades can cast a moving shadow on nearby buildings. This is called “shadow flicker.” The American Wind Energy Association says wind power plant developers can calculate whether a flickering shadow will fall on a given location near a wind farm and how many hours in the year it will do so. This makes it possible for developers to erect turbines in locations that won’t cast a shadow on houses. People who live near turbines that cast shadows on their homes often say the flickering is irritating—one US farmer whose home is located 900 feet/274 meters from a wind turbine with 122-foot/37-meter blades compared it to a light switch being flipped on and off for hours at a time.
History of Wind Energy
Wind energy propelled boats as early as 5000 B.C. By 200 B.C., simple windmills in China pumped water, while vertical-axis windmills with woven reed sails were grinding grain in Persia and the Middle East. By the 11th century, people used windmills for food production.
5000 B.C. – Ancient Egyptians use wind energy to propel boats along the Nile River.
200 B.C. – The Chinese use simple windmills to pump water, and people in the Middle East use vertical-axis windmills with woven reed sails to grind grain.
11th century – After seeing people in the Middle East using windmills for food production, European explorers take the technology home with them. The Dutch use this new technology to drain lakes and marshes in the Rhine River Delta.
Late 19th century – In the US, windmills are used to pump water for farms and ranches.
1890 – Wind turbines that can generate electricity are introduced in Denmark.
1930s – As industrialization picks up, the steam engine replaces water-pumping windmills in Europe.
1940s – A large-scale wind turbine is introduced in Vermont, providing electricity for several months during World War II, when fossil fuel prices were high. When fossil fuel prices fell after the war, interest in wind power waned.
1970s – Fuel prices skyrocket as the result of oil embargoes, and interest in improving on wind turbine technology picks up. Wind turbines are made safer and quieter.
Today – Wind power plants—or “wind farms”—generate power across the US and Europe, and with continuing research and development, wind-generated electricity is comparable in cost to other power sources.
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