Old wooden windmills

Until recently, she was considered a "native" of China; it is more likely that it came from the highlands of Iran or from Tibet. The first windmills launched into operation had sails rotating in a horizontal plane around a vertical axis. The reed or cloth covered sails ranged from 6 to 12. These mills were used to grind grain or extract water and were quite different from later European vertical wind mills.

Tower windmills appeared by the end of the 13th century. Their main advantage was that in the tower mill only the roof of the tower was reacting to the presence of wind. This allowed the main structure to be made much higher, and the blades larger, thanks to which the rotation of the mill became possible even with light wind.

In the Mediterranean countries, tower mills were built with fixed roofs, because the change in wind direction most of the time was very small.

Most windmills had four sails. Along with them there were mills equipped with five, six or eight sails. They are most common in the UK, Germany and less often in other countries. The first plants for the production of canvas for the windmills were located in Spain, Portugal, Greece, Romania, Bulgaria and Russia.

Many centuries ago they began to be used for grinding grain, as a drive for a water pump, or for both. In Holland, the windmills have found the most active use in connection with the natural and climatic conditions of the country - the need to pump water from low-lying areas and the presence of strong sea winds.

Great importance in windmills has always had the design of the blades (sails). Traditionally, the sail consists of a frame-lattice, on which the canvas is stretched. Miller can independently adjust the amount of tissue depending on the strength of the wind and the required power. In colder climates, the fabric was replaced with wooden slats, which prevented freezing. Regardless of the design of the blades, to adjust the sails, it was necessary to completely stop the mill. The turning point was the invention in Great Britain at the end of the 18th century of a structure that automatically adapted to wind speed without the intervention of the miller.

The sails, invented by William Kabitt in 1807, became the most popular and functional. In these blades, the fabric was replaced by a mechanism of connected shutters. In the twentieth century. Thanks to advances in the aircraft industry, the level of knowledge in the field of aerodynamics significantly increased, which led to a further increase in the efficiency of the windmills by the German engineer Bilau and the Dutch masters.

There were also wind pumps. They were used to pump water on the territory of modern Afghanistan, Iran and Pakistan since the 9th century. The use of wind pumps has become widespread throughout the Muslim world, and then spread to the territory of modern China and India. Wind pumps were used in Europe, especially in the Netherlands and the regions of East Anglia of Great Britain, starting from the Middle Ages and further, when draining land for agricultural work or for construction purposes.

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