An historical approach to the Wind Energy

Navigation of the Mediterranean Sea began in Egypt more than 6.000 years ago, along the Nile River, down wind. Alongside the pyramids, buried sailboats were found, they were meant to help the buried pharaohs in their trip to the afterlife.

Thereafter, Egyptians started building ships which sail permitted the navigation against the wind, what permitted the maritime navigation.

The wind use for the maritime transportation began with the big civilizations in the ancient times. There is knowledge of its use in Mesopotamia due to a model in clay of a small sailboat.

Boat for the river navigation (Tomb of Menna) 

The Greek culture and its mythology considered the natural forces (fire, water, wind) an exclusive domain and use of the Gods, and that they did not take the intromission in their domains very well. This mythological concept of nature did not help to the technical development. Besides, there was not the imperative need nor means to carry out the development of machinery pushing for an improvement in the production methods because its economy was based in an agriculture of subsistence, the low commercial exchange and existence of a social structure where the slave work was abundant. These facts did not aid the technological development.

The political stability and the economical growth in the big cities of the Greek Empire promoted the major cultural development of the Hellenic culture. It is in the III century BC and in Alexandria when Ctesbio invented several devices that worked powered by water and air. Hydraulis or, hydraulic organ, work in such a way that the water and the air enter in a compartment located in the upper part of the wind camera, and from there, it is distributed to the pipes of the organ.

Once separated from the air, the water is evacuated from the wind camera. Then, the water pushes a wheel, which, at the same time, moves a musical cylinder. To make the organ work, the key that permits the flow of water inside the instrument must be opened (it is what makes the water to flow continuously).

Modern reconstruction of hydraulis Heron of Alexandria

Middle Age

After the fall of the Roman Empire, and the later barbarian invasions, there was no knowledge of the use of the windmills, therefore the ignorance of the wind technology in this era was more than obvious. In the middle ages, the use of watermills with river currents was commonly used to move mechanisms of grain milling.

In the Arabic culture and in the Persian region is where the first evidence of skilled use of the wind to move millstones of its windmills was found. To the date only blood mills had been used, these were powered by animal or slave traction to mill the grain.

The rise of the big Persian cities and the consequent depopulation of the rural areas induced this change of driving forces of the mills.

Windmills in the Iranian region of Nishtafun

These first Persian mills, were made of Wood. They were vertical axis devices around which the blades rotated. It avoided the turbulences produced by the changes in the wind direction through the protection of the blades in a big hole, where the air entered thus eliminating the turbulence.

The clay construction that surrounded the system of blades contributed to the generation of currents due to the difference of pressures between the internal and external faces.

Operating principle of a persian windmill

In the northeastern of the region of Jarasan currently exist batteries of these windmills that can mill about 3000 kilograms of wheat per day. In these vast and dry plains, the wind can blow uninterruptedly during months in the same direction, in such a way that the installation of a big number of mills results highly profitable. This area is known as “the country of the 120 days of wind”.

The horizontal axis mills had also arisen in the old Persia, probably before the Islamic period. Technologically, it is easier to take advantage of the wind energy with a horizontal wheel, but its invention responded to the needs of adapting the vertical axis wind machines for the purpose of pumping of water. The disposal of the rotor, in the horizontal axis systems, is more suitable to move a fair wheel without having to vary the direction of the driving force through a gear, which, without doubts, was a technical difficulty for that time.

Meanwhile, in the Far East, the Chinese had been using long time ago mills called Panemonas, which were used to pump the water and the irrigation. This Chinese mills were vertical axis ones, made of wood or bamboo. The blades could vary its position depending on the direction in which the wind blew. There is proof of its existence previous to 400 century AD, therefore, they can be considered precursors of the vertical axis Persian mills.

There is not very much data available regarding vertical axis windmills form the medieval Europe, they were a used to grind grain before the end of the XII century AD.

The diffusion of the windmill in the Mediterranean region were very probably due to the expansion of the Islamic civilization, arriving up to the Iberian Peninsula. In this area, the typical Mediterranean mill was developed in several different typologies attending to the number and shape of blades.

 Manchego and greek windmills

On the other side, it is possible that the crusaders were who brought from Palestine these mechanical wits to the northwestern zone of the region: Britain, England and Netherlands, between the XI and XII centuries AD. There are other theories, which support that Europe had the technical capacity to develop windmills from the improvements performed in the hydraulic mills, having developed the horizontal axis mill in Occident before the Crusades.

Dutch windmill

The Northwest mill called the Holland mill or pivot, which was characterized by its construction materials: almost completely out of wood. Its mechanism is inside the body being normally quadrangular. Those mills turn around its lower axis.

The characteristics of the Mediterranean mills are different from the Dutch. The body is cylindrical, made of masonry instead of wood, being the ceiling the element that turn in the wind direction for a better wind achievement.

Due to the feudal system that rules the society of that time, the religious orders, the abbeys or the rural nobility who controlled the monopoly of the transport, grind and distribution of the grain and flour. It was even forbidden to plant trees near the mills to ensure the free incidence of the wind over the blades.

In Holland, in the year 1340, they used windmills for the first to drain water of the wetlands and, in that way, win terrain to increase the breeding grounds. For this purpose, at the end of the XVI century emerged in Holland and Germany a new type of mill whose only purpose was to drain water. It is called the tjasker: it consists of a mast, which has the blades in one end and an Archimedes´ screw on the other end, avoiding the inclusion of any other type of mechanism.

Dutch Tjaster