Credited to Iran. The date is uncertain: the designs are described as about 1,000 years old, while Iran's UNESCO submission claims far earlier use. Sistan spans present-day Iran and Afghanistan, and one historian cited by UNESCO calls the early windmill a device of Iran and Afghanistan.
How it began
The first windmills, locally called asbads, appear to have originated in Sistan, in the east of present-day Iran. Strong northern winds blow there through spring and summer, known as the 120-day winds, and water was scarce. According to Iran's submission to UNESCO, steady wind and lack of water power led people of the region to grind grain with the wind. The submission cites Joseph Needham, who held that the history of windmills began in Iran, and the technology historian Robert Forbes, who called the windmill of the Islamic era an Iranian invention.
How it works
An asbad is a two-story structure of mud brick, clay and wood. The sails stand on the upper level and the millstones sit on the floor below. Wind enters through an opening and pushes the sails around a vertical wooden shaft, which turns the millstone directly. Because only one side of such a rotor can take the wind while the other moves against it, the mills are shielded on one side, and the blades can never move faster than the wind. Mills were built in rows on the highest ground, sometimes 40 side by side.
How it spread
Forbes wrote that the device, at first exclusive to Iran and Afghanistan, became an important source of power across the Islamic lands in the 12th century, used for grinding grain, pumping water and crushing sugarcane. Vertical-axis windmills were taken to China during Mongol rule and were used in Egypt for sugarcane. Iran's submission states that the technology reached Europe around 1105, where the axis was changed to a near-horizontal one.
What lasted
The rows of mills also served as windbreaks that sheltered nearby villages from storms. Wind remained a common source of mechanical power for grinding grain and raising water until the early 20th century, when engines burning fossil fuel replaced it. The vertical-axis layout survives in some modern wind turbines, which keep the generator near the ground for easier maintenance.
Where it stands today
The windmills of Nashtifan, near Khaf in northeastern Iran, are made of clay, straw and wood and have been milling grain for an estimated 1,000 years. National Geographic reported in 2017 that without regular attention they may stop turning. Iran has placed the asbads on its tentative list for World Heritage status.
