Winds are caused by the uneven heating of the atmosphere by the sun, the irregularities of the earth's surface, and rotation of the earth. Wind flow patterns are modified by the earth's terrain, bodies of water, and vegetative cover. This wind flow, when "harvested" by modern wind turbines, can be used to generate electricity.
The term wind energy describes the process by which the wind is used to generate mechanical power or electricity. Wind turbines convert the 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 to power homes, businesses, schools, and other facilities.
Most wind turbines turn in the moving air like aircraft propeller blades, and power an electric generator that produces an electric current. A wind turbine is essentially the opposite of a fan: instead of using electricity to make wind, like a fan, wind turbines use wind to make electricity. The wind turns the blades, which spin a shaft, which connects to a generator and makes electricity.
Modern wind turbines fall into two basic groups; the horizontal-axis variety, like the traditional farm windmills used for pumping water, and the vertical-axis design, like the eggbeater-style Darrieus model, named after its French inventor. Most large modern wind turbines are horizontal-axis turbines.
"Wind power also has the advantage that it can be deployed faster than other energy supply technologies. Building a conventional power plant can take 10 or 12 years or more, and it is not producing power until it is fully completed. Wind power deployment is measured in months, and a half completed wind farm is just a smaller power plant, starting to generate power and income as soon as the first turbine is connected to the grid. Even large offshore wind farms, which require a greater level of infrastructure and grid network connection, can be installed from start to finish in less than two years, a crucial asset given the pressing threat of climate change."