Category: Wind

From massive wind farms generating power to small turbines powering a single home, wind turbines around the globe generate clean electricity for a variety of power needs.

In the United States, wind turbines are becoming a common sight. Since the turn of the century, total U.S. wind power capacity has increased more than 24-fold. Currently, there’s enough wind power capacity in the U.S. to generate enough electricity to power more than 15 million homes, helping pave the way to a clean energy future.

WHAT IS A WIND TURBINE?

The concept of harnessing wind energy to generate mechanical power goes back for millennia. As early as 5000 B.C., Egyptians used wind energy to propel boats along the Nile River. American colonists relied on windmills to grind grain, pump water and cut wood at sawmills. Today’s wind turbines are the windmill’s modern equivalent — converting the kinetic energy in wind into clean, renewable electricity.

HOW DOES A WIND TURBINE WORK?

The majority of wind turbines consist of three blades mounted to a tower made from tubular steel. There are less common varieties with two blades, or with concrete or steel lattice towers. At 100 feet or more above the ground, the tower allows the turbine to take advantage of faster wind speeds found at higher altitudes.

Turbines catch the wind’s energy with their propeller-like blades, which act much like an airplane wing. When the wind blows, a pocket of low-pressure air forms on one side of the blade. The low-pressure air pocket then pulls the blade toward it, causing the rotor to turn. This is called lift. The force of the lift is much stronger than the wind’s force against the front side of the blade, which is called drag. The combination of lift and drag causes the rotor to spin like a propeller.

A series of gears increase the rotation of the rotor from about 18 revolutions a minute to roughly 1,800 revolutions per minute — a speed that allows the turbine’s generator to produce AC electricity.

A streamlined enclosure called a nacelle houses key turbine components — usually including the gears, rotor and generator — are found within a housing called the nacelle. Sitting atop the turbine tower, some nacelles are large enough for a helicopter to land on.

Another key component is the turbine’s controller, that keeps the rotor speeds from exceeding 55 mph to avoid damage by high winds. An anemometer continuously measures wind speed and transmits the data to the controller. A brake, also housed in the nacelle, stops the rotor mechanically, electrically or hydraulically in emergencies. Explore the interactive graphic above to learn more about the mechanics of wind turbines.

TYPES OF WIND TURBINES

There are two basic types of wind turbines: those with a horizontal axis, and those with a a vertical axis.

The majority of wind turbines have a horizontal axis: a propeller-style design with blades that rotate around a horizontal axis. Horizontal axis turbines are either upwind (the wind hits the blades before the tower) or downwind (the wind hits the tower before the blades). Upwind turbines also include a yaw drive and motor — components that turns the nacelle to keep the rotor facing the wind when its direction changes.

While there are several manufacturers of vertical axis wind turbines, they have not penetrated the utility scale market (100 kW capacity and larger) to the same degree as horizontal access turbines. Vertical axis turbines fall into two main designs:

• Drag-based, or Savonius, turbines generally have rotors with solid vanes that rotate about a vertical axis.
• Lift-based, or Darrieus, turbines have a tall, vertical airfoil style (some appear to have an eggbeater shape). The Windspire is a type of lift-based turbine that is undergoing independent testing at the National Renewable Energy Laboratory’s National Wind Technology Center.

WIND TURBINE APPLICATIONS

Wind Turbines are used in a variety of applications – from harnessing offshore wind resources to generating electricity for a single home:

• Large wind turbines, most often used by utilities to provide power to a grid, range from 100 kilowatts to several megawatts. These utility-scale turbines are often grouped together in wind farms to produce large amounts of electricity. Wind farms can consist of a few or hundreds of turbines, providing enough power for tens of thousands of homes.
• Small wind turbines, up to 100 kilowatts, are typically close to where the generated electricity will be used, for example, near homes, telecommunications dishes or water pumping stations. Small turbines are sometimes connected to diesel generators, batteries and photovoltaic systems. These systems are called hybrid wind systems and are typically used in remote, off-grid locations, where a connection to the utility grid is not available.
• Offshore wind turbines are used in many countries to harness the energy of strong, consistent winds found off of coastlines. The technical resource potential of the winds above U.S. coastal waters is enough to provide more than 4,000 gigawatts of electricity, or approximately four times the generating capacity of the current U.S. electric power system. Although not all of these resources will be developed, this represents a major opportunity to provide power to highly populated coastal cities. To take advantage of America’s vast offshore wind resources, the Department is investing in three offshore wind demonstration projects designed to deploy offshore wind systems in federal and state waters by 2017.

FUTURE OF WIND TURBINES

To ensure future growth of the U.S. wind industry, the Energy Department’s Wind Program works with industry partners to improve the reliability and efficiency of wind turbine technology, while also reducing costs. The program’s research efforts have helped to increase the average capacity factor (a measure of power plant productivity) from 22 percent for wind turbines installed before 1998 to more than 32 percent for turbines installed between 2006 and 2012. Wind energy costs have been reduced from more than 55 cents per kilowatt-hour (kWh) in 1980 to under 6 cents/kWh today in areas with good wind resources.

Wind turbines offer a unique opportunity to harness energy in areas where our country’s populations need it most. This includes offshore wind’s potential to provide power to population centers near coastlines, and land-based wind’s ability to deliver electricity to rural communities with few other local sources of low carbon power.

The Energy Department continues working to deploy wind power in new areas on land and at sea and ensuring the stable, secure integration of this power into our nation’s electrical grid.

Wind energy is the latest non-solar energy source, which is widely used. In many parts of the United States, the wind’s patterns and speeds vary because of the differences in terrain, vegetation, presence and size of water bodies (Aissaoui and Tahour 31). Wind power has many purposes in daily living, including electricity, kite flying, and sailing. The future tends to clean energy, and wind energy is an inevitable option, as Colorado has been the first government to adopt it (Finley). Many other states are investing in this technology for its numerous benefits. For example, although China’s primary electricity source is coal, the country is considering wind power for small-scale use (Aissaoui and Tahour 33). Therefore, due to the rising popularity of wind turbines, there is a need to explore how they work, their benefits, and limitations.

Wind turbines, through their rotor blades, convert wind energy into electricity. This is achieved through aerodynamic force and velocity sensors, which enhance the performance of this technology (Learn Engineering 2015). When the wind blows across the turbines, it decreases the air pressure on one side of the edge while increasing the other, creating a “lift and drag” effect (Woodford). This impact causes the blades to spin faster with a rise in the strength of the wind. This continuous aerodynamic translation and faster rotation of the turbines, connected to a generator, create electrical energy.

Although wind energy technology has been identified for the future, it has many benefits. One of them is cost-effectiveness since it is one of the lowest-priced sources of energy. It also produces clean energy because it does not contaminate the environment as power plants do, burning fossil fuels (Ng and Ran 112). Another advantage is that it does not hinder farmland operations, which significantly benefits the rural economy since work can be continued in ranches and farms because of the small fraction of the land which wind turbines require.

One of the limitations is that wind is not strong enough to produce a substantial amount of electrical energy. This technology is not effective in running many operations which require electricity (Ng and Ran 117). Moreover, wind turbines pose a danger to some animals, for example, bats and flying birds. If these creatures run into the rotor blades, they may be injured or killed. Lastly, they are noisy, which is why they are mostly located in rural areas (Ng and Ran 118). Turbines produce disturbing sounds, prompting the development of designs aimed at reducing this effect.

The winds of Santa Ana, as explained by a well-respected author, Joan Didion, occur on a hill of a mountain and shift from cold air to a dry and humid wind as it travels down the mountains into Los Angeles. At the beginning of Didion’s story “Los Angeles Notebook,” she emphasizes that the Santa Ana winds can be very dangerous and have very negative effects. Didion’s unpleasant feelings toward the Santa Ana Winds are depicted through the tone and imagery.

Didion uses tone to demonstrate the mysterious feeling of how the social atmosphere changes as the Santa Ana winds flow into Los Angeles. An example of this is at the beginning of her story the tone is negative and abnormal using words like “screaming”, “unnatural”, and “tension”. Didion uses spooky words and opinions in the beginning to sway and enthuse the reader. At the end of Didion’s story, she changes the tone to inform the reader more about the Santa Ana winds. One more example of tone is towards the end of her story she talks about the wind being similar to the “foehn wind” which is common in Switzerland “in Switzerland the suicidal rates go up and crime rates increase during the foehn winds” making the tone informative. Didion compares the foehn wind with the Santa Ana wind to show that both winds have the same unhappy effect on people. Didion uses this tone to help educate people on the Santa Ana winds and the side effects that take place when the winds flow in.

Didion uses visual imagery to convey the mysterious feeling that various people have when the Santa Ana winds blow into Los Angeles. An example of this is where Didion talks about when she saw the next-door neighbor walking around outside their house with the lights off and a machete in hand because he heard an intruder. Didion shows that the Santa Ana winds have a mesmerizing effect on everyone including her neighbor. In hindsight, the wind brings many abnormal changes to the social environment. Another example of imagery is “but by the eerie absence of surf”, and how the heat outside was making it unbearable. Didion emphasizes that the Santa Ana winds bring in heat that people cannot stand and are forced to stay indoors and antisocial. This demonstrates visual imagery by saying that because of the Santa Ana winds that there would be nobody surfing, as the winds bring a depressed mood amongst many people.

This sonnet is written by Percy Bysshe Shelley. P.B. Shelley was amongst the main English Romantic poets. One of his best-known (familiar) works is ‘ Ode to the West Wind. ‘Additionally, the metaphors that are manipulated in this sonnet are clear examples of this fact.

Metaphors in This Poem

‘O wild West Wind, thou breathe of Autumn’s being’ In the first line, the autumn is seen as a human being that can breathe. The breath of autumn is the wind of the west. There are two metaphors in this line. The Autumn is that human being and The Wild West Wind is a human. As opposed to ‘breath’ and which maintains Autumn, this metaphor gives the west wind approximately mystical meaning. The narrator indicates that the west wind is most probably synonymous with Autumn.

The second line is a used metaphor. Leaves are emphasized as dead. Death depends on human experience, and here Leaves are qualified as a human beings. And also in the fourth line, it is mentioned that the Leaves are ‘pale and hectic.’ These words describe human beings and are metaphorical.

There is a metaphor inline six. ‘Dark wintry bed’ is referred to the grave of the leaves. The poet emphasized that the grave is a bed and death is sleep. The grave and dark are pretty cold like winter.

In the seventh line, The winged seeds, where they lie cold and low, define the seed condition in the soil after the sweeping is made by the west wind. Wings are like angels and the seeds are reflected vividly. This is another metaphor and the poet described plants as living.

Spring thunder is described as the clarion of the spring breeze in ‘Her clarion o’er the dreaming earth’ Since a clarion is a sort of instrument and living things are almost always the owner of it in particular, Therefore, this ninth line has a metaphor. That is, the Wind is expressed as a human.

Bases of comparison in this poem

Shelley compares it to the minimal life we are granted on the planet. The wind is a common force of the ‘West Wind’ which helps the leaves to fly until their death. The wind is strong and presents a kind of freedom.

There is a simile in the third line. This simile is a comparison of dead leaves to ghosts. The poet emphasized that dead leaves are terrible like ghosts.

‘The winged seeds, where they lie cold and low,

Each is like a corpse within its grave, until

Thine azure sister of the Spring shall blow

There is a metaphor in the seventh line. This metaphor is the comparison of seeds to flying creatures.

The narrator extends the metaphor of the leaves as the dead by describing that the wind takes them and ‘winged seeds’ to their graves, ‘where they lie cold and low.’ Then to compare each leaf to a corpse within its grave’ the speaker uses a simile. This simile is the comparison of each seed to a corpse. The narrator states that until the winds come in, each is like a ‘corpse’, carrying away the dead but offering a better beginning. The use of the term ‘azure’ to characterize the wind (breeze) compares strongly with the colors used to define the leaves.

There is a personification in lines 9-10. This personification is the comparison of spring wind to a person. The spring wind has the feature of making sound, so it has been compared to human beings. And also line 10 has metaphor and personification. This line is a comparison of the earth to a dreamer. According to this line, the earth can sleep, wake up and dream like a human.

Finally, there is a simile in line 11. This simile is a comparison of buds to flocks. The poet compares a farm pushing flocks of sheep with a simile ‘Driving sweet buds like flocks to feed in the air’ with the spring storm catalyzing the flowers into full bloom.