Wind power is the conversion of wind energy into a useful form of energy, such as using wind turbines to make electricity, windmills for mechanical power, wind pumps for water pumping or drainage, or sails to propel ships. The total amount of economically extractable power available from the wind is considerably more than present human power use from all sources. Wind power, as an alternative to fossil fuels, is plentiful, renewable, widely distributed, clean, and produces no greenhouse gas emissions during operation, and the cost per unit of energy produced is similar to the cost for new coal and natural gas installations.
Wind turbines, like windmills, catch the wind's energy with propeller-like blades. These blades can have a horizontal axis, like a fan, or vertical one, like a merry-go-round. The most common design is a tall tower with three large blades on a horizontal axis. But some vertical-axis wind turbines look like eggbeaters, while others look like the windmills that populated farms a century ago.