A bit of history: hydroelectric

Thousands of years ago mankind learned how to exploit the mechanic energy produced by falling water. The Greeks and Romans already used water mills to grind wheat. In Barbegal, France, and near Arles, an important port supplying Rome with wheat, 8-wheel water mills were found exploiting the same river at the same time (310 A.D.). However, in Europe the exploitation of water power to obtain mechanic work was to become more common only during the 12th and 13th century. The main use was in the agricultural sector, i.e. grinding cereals, olives, salt and other minerals by means of water mills. Other machines powered by canals were developed between 1500 and 1600, although they were less common than water mills. One of the best manufacturers of this kind of machines was Leonardo da Vinci. During the Middle Ages the water wheel invented by the Greeks became very popular. It was a sort of mill used to lift water and was used to reclaim swamp areas, to irrigate and in the mining field. The water wheel coupled with a camshaft (part of a machine that, fixed to a rotating axis, transmits a continuous rotating movement to another part of the machine by making it alternatively lift and lower) also allowed the production of an alternated vertical movement, similar to a hammer. It was used to print textiles and operate bellows, leading to a further development of the metal industry. Great technical progress was achieved following the evolution of the water wheel into the turbine, i.e. an equipment capable of transforming mechanic energy into electric energy. The creation of the hydraulic turbine dates back to the end of the 1800s. Since the earlier times, this technology has been improved further, and today the total yield of the more modern plants is over 80%. This means that if the energy of water is equal to 100, the useful energy supplied by a hydroelectric power plant is equal to 80.

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