Wind is created by uneven heating of the Earth's surface from the sun. This causes warm air to rise over land and cooler air to move in, creating wind. Modern wind turbines convert the kinetic energy of wind into electricity. The most common design has two or three horizontal propeller-like blades atop a tall tower to capture wind energy and convert it to mechanical power. Large wind farms require average wind speeds of 13 mph while small turbines require 11 mph to efficiently generate electricity. Wind turbines were developed to provide renewable energy without emissions in response to energy shortages and environmental concerns.

1. Wind Energy By: Alex Sloan

2. How Wind is Created Wind is created by the uneven heating of the Earth’s surface by the sun. In the day, the air over land heats quicker than the air over water. The warm air over the land expands and rises, and the cooler air, which is heavier, takes its place, creating wind. In the night, the wind’s direction is reversed because the air cools quicker over land than over water. This is called the daily wind cycle.

3. Wind Turbines Wind can be used to generate electricity with modern wind turbines. Wind turbines convert kinetic energy in the wind into mechanical power.

4. Wind Turbine Design The most common design has two or three propeller like blades that rotate around a horizontal axis mounted at the top of a tall tower, land the blades capture the energy from the wind. The picture on the right is an example of the most common design. The second design has the blades that rotate around a vertical axis, rather than a horizontal axis. It looks similar to an upside down eggbeater.

5. Requirements for wind energy generation through Turbines Large wind farms require an average of 13 miles per hour in order to efficiently generate electricity. Small wind turbines require an average of 11 miles per hour to generate electricity efficiently. Many places in the world meet these wind speed requirements.

6. Why we use Wind Turbines In the 1970s, there were energy shortages, and in the 1980s, there were concerns about the environment, so people became interested in generating energy with wind turbines because there is no fuel required to burn, and there are no harmful emissions or waste products.

7. Wind Energy Applications Applications of wind energy can be used for small households, or massive provincial and national networks. It is accepted in a wide range of uses because it is renewable, so it is mostly accepted over coal and fossil fuels.

8. Wind Energy Facts Wind energy has been used to fill sails and move ships through the sea for a long time. The windmill was invented in around 200 BC, then for farming, but now for generating electricity. In 2008, Denmark produced 25% of its energy from wind. Between 2001 and 2007 the amount of electrical energy produced from wind power quadrupled. In 2008, wind machines in the United States generated a total of 52 billion kilowatt-hours, about 1.3% of total U.S. electricity generation.