A windmill is a structure or machine that converts wind into usable energy through the rotation of a wheel made up of adjustable blades. Windmills are fairly simple: Wind turns the blades, the blades turn an electric generator, and the electric generator produces electricity.
Traditionally, the energy generated by a windmill has been used to grind grain into flour. Windmills are designed by skilled craftsmen and can be constructed on site using hand tools. Windmills were first used in Persia, in modern-day Iran. Windmills were also traditionally used in Holland and in 19th- and 20th-century America.
Windmills developed steadily over the centuries and achieved their most prominence in Europe during the eighteenth century. They were largely replaced as a power generating structure when steam power was harnessed during the nineteenth century. Today, windmill technology is experiencing a renaissance and the wind turbine promises to be an important alternative to fossil fuels in the future.