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Strong northern winds (Shamal) blow throughout the year in the eastern parts of Iran (Sistan and Baluchistan, Southern Khorasan and southern parts of Razavi Provinces). Though this natural phenomenon is more prevalent all over the country during autumn, and in winter, winds may keep blowing, but the eastern parts of Iran are an exception in that even when there is no wind in other parts of Iran during spring and summer, these parts are affected by winds known as "120 days winds / black winds" the speed of which sometimes gets to 100 km / hour. The endless wind almost all over the year along with the scarcity of water resources were two factors which encouraged our ancestors to make an efficient use of this natural energy, as a result of which windmills locally called "Asbad" were invented.
Asbad is one of the most significant architectural structures of Iran in its desert regions which converts kinetic energy of air (wind) into other forms of energy.
Asbad is a smart technique to grind grains, a technique which goes back to ancient times when the people living in the eastern parts of Iran in an attempt to adapt themselves with the nature and transform environmental obstacles into opportunities managed to invent it. Iranian architects' smart utilization of a natural threat i.e. strong and annoying winds and rendering it to an exceptional opportunity for the production of a strategic product like bread is not short of a miracle.
As a result of abundant and free of charge energy of wind in parts of the eastern region of Iran, one can see 40 windmills built side by side without any worry that energy may one day run out. During the 120 days winds period, winds pass through the wind catcher openings and rotate the wheels and vanes, the heavy weight of the milling machinery and wheel is exerted on the axis and rotates the millstones.
The windmills are designed in such a way that winds encounter no obstacle to reach them, as a result of this concern, windmills are built on high elevations. To make the optimal use of the wind, all the uniform windmills of a village or town used to be concentrated at a single location on the highest spot of that area. Another reason for this strategy related to the fact that since all the windmills were built as a complex plant in a single area which sometimes stretched over an area of 1 km wide, it acted as a barrier against the annoying storms for the nearby villages / towns. Therefore, it served two useful functions: grinding grain and protecting the village / town against storms.
The two story windmills designed horizontally had vertical axis and the wood, mud and brick were the main construction materials.
Historical Overview: Man's use of wind goes back to 3000 years ago. The first evidence for this claim can be found in Iran and China. Simple turbines used at that time had mostly vertical axis. Up to the beginning of 20th century, wind was often used to generate mechanical energy to draw up water or grind grains.
With the industrial revolution, fossil fuel powered engines replaced wind in an attempt to provide the industries with a more stable source of energy. However, in the start of the 1970s with the first oil price shock, once again the use of wind energy was given priority.
The first Asbads seem to have been originated in Sistan. In fact, the invention of Asbad (windmill) in that region was a kind of adaptation with the special conditions of the region which did not have sufficient water but enjoyed abundant and non-stop wind blowing. Joseph Needham maintains that the history of windmills originated in Iran as a part of Islamic culture.
Robert Forbes, a technology historian, stresses the point that Islamic era windmill was in fact the invention of Iranian. He writes: "this invention which was initially an exclusive device for Iran and Afghanistan, turned into an important source of energy all over the Islamic territories in 12th century and not only it was used for the grinding of grains and operation of water pumps, but also for the chopping of sugarcanes and other purposes.
Vertical-axis windmills which are known as "Iranian windmills" were taken to China during the Mongol reign. These windmills were also taken to other Islamic territories and were used in Egypt as a main source for the chopping and grinding of sugarcanes. In 11th century, windmills reached Spain, the Islands of Aegean Sea and Portugal, but it had been slightly modified and its vertical axis had been changed to horizontal axis with a 30 degree slope. Many historians hold that Iran has been the birthplace of vertical-axis windmills and it was in 1105 AD. when this technology found its way to Europe.
The different traditional samples of Iranian architecture show that this kind of architecture has always turned towards ecological and social sustainability along with respect for natural resources and their preservation for posterity. Attention to the inexhaustible energy sources such as sun, wind, and their use for the improvement of living conditions has had a long history in Iran. The use of wind as a modified form of solar energy has had a long history in the arid areas of Iran. Structural elements such as Asbads which are compatible with environmental, climatic conditions and ecological capacities are unique and outstanding examples for this claim. Asbad is a self-revealing example for a local creative thought which has wisely made use of the existing potentials of the region to fulfill the needs of local communities. This technology in its entirety is a local phenomenon. All the factors effective in the construction and function of this device are local orientated, a phenomenon which is still dynamic and alive. The materials needs for the building of each individual part and also the workforce for the construction and operation of Asbad and even the layout methods give it a unique and outstanding value.
Criterion (i): Iran has been one of pioneers in the use of clean energy. The creative ingenuity in harnessing natural forces such as wind, underground or runoff waters has clear examples in the farthest periods of architectural and social history of Iran, Asbad being one of them. With its hidden enigmas, the traditional architecture of Iran was able to provide the key for the communities' needs, communities which faced a plethora of shortcomings and climatic hazards. By making use of centuries old experiences, these communities managed to turn the threats into golden opportunities for themselves. Asbad is one of the samples displaying Iranian innovative ingenuity which has been erected in windy parts of the country (Sistan and Baluchistan). It is the most efficient method for the use of clean energy (wind) and it depicts the ingenuity of the communities living along the desert to deploy the natural forces and adapt themselves with them, it is a masterpiece and a good example of human ingenuity.
Criterion (iv): Asbads as a unique industrial, architectural sample of Iran is in fact a mechanical machine which converts wind energy into other forms of energy. The nature of this integrated architectural structure was a kind of technological mutation in the use of wind energy. Asbads are exclusive Iranian structures which despite their simple mechanism enjoy a wise and methodical design, enabling them to control destructive winds and turn them useful.
Criterion (v): Technically and technologically, windmills from Sistan to khorasan, are outstanding examples of a technical, architectural collection, forming an exceptional landscape which is considered as an important phase in development of human knowledge and technology. Furthermore, using earthen materials and plants demonstrate this system interaction with its environment. Asbads are a clear example for concerns for natural resources and their preservation in order to engender prosperity and comfort, without endangering the environment. It is a perfect example for man's ingenuity and innovation to improve human life by creating aerodynamic property in order to better absorb wind energy. The use of locally available and abundant materials in the area and the use of renewable energy by converting it to mechanical energy to grind grains and the use of local plants for the covering of the sails are all indicative of the environment-friendly nature of asbads.
Asbads are two story structures where millstones are placed in the ground floor and sails on the first floor. This overall format of asbads has been preserved and developed over time in different parts of the country. The main materials used for the building of asbads can be obtained locally. Mud-brick and clay are easily available in the place and millstones of at most 900 kg weight are brought from nearby mountains. The vertical axis is made of durable, long-lasting wood. Other construction tools required for Asbad are also available in the location, so there is no need for the import of materials or tools.
Asbads' main function has been grinding grains since early times up to now. To make the best use of wind force, windmills are often placed at the highest spot and no other construction is allowed to be made before them. This strategy can be seen in all the location where asbads can be found.
Urbanization and city expansion are inevitable, however due to the high value of asbads for the communities, city expansion has been pursued with suitable respect for the Asbads of each territory. Consequently, despite the passage of centuries, because of the local peoples' special attention to them, Asbads have managed to preserve their integrity and authenticity.
Windmills are of two major categories, Iranian and European. European windmills appeared in 10th and 11th century as a result of east and west confrontation on the basis of Iranian windmill which was operational in Iran since the 2nd century. There are several distinctions between the two which can be listed as architectural and technical:
In the Iranian samples of windmills, like the sample seen in Nashtifan Village (in the vicinity of Khaf city), the sails of the windmill rotate on a vertical axis, therefore releasing the structure of unnecessary weight of sails, so it can be devoted to other functions. Perhaps it has been the factor behind turning Iranian windmills as one of the most dynamic forms among its ancient counterparts. In the different windmills operated in the eastern parts of Iran, wind energy is directly transferred to millstones by means of vertical axis sail.
The European model of windmills known as "Kinderdijk" in Netherland have horizontal axis and are in the form of a tower using a simple mechanism for the holding of sails and wind energy transfer to millstones. Due to the architectural design and the mechanism of sails function, European windmills cannot easily be integrated into the modern urban system, but Iranian windmills by using vertical axis rotation of vanes (sails) can operate in accordance with the wind velocity and intensity. Moreover, they can act as a wind breaker when cities or residential complexes are at stake by strong winds.
The windmill of Nashtifan village is still operational even after hundreds of years, whereas non-functional windmills of Kinderdijk are now just a tourist attraction site.
Windmills of Zaanse Schans in Netherland and Mykonos windmills of Greece are other European windmills which can be studied for comparative purposes.
ZaanseSchans is a protected zone besides Zaan River in the northern parts of Zaandam in Netherland. This region displays traditional architecture which date back to 17th and 18th centuries. There are several windmills in this region which serve various purposes including logging wood, grain thrashing and processing oilseeds.
The five windmills of Mykonos are the first sites that one can see as the ship approaches the harbor. There are a total 16 windmills in Mykonos many of which were built by Venetians in 16th century to grind wheat. These windmills have stopped operating since mid 20th century.