Places where it was developed
Contenido
La primera central hidroeléctrica moderna se construyó en 1880 en Northumberland, Gran Bretaña. El renacimiento de la energía hidráulica se produjo por el desarrollo del generador eléctrico, seguido del perfeccionamiento de la turbina hidráulica y debido al aumento de la demanda de electricidad a principios del siglo . En 1920 las centrales hidroeléctricas generaban ya una parte importante de la producción total de electricidad. En todo el mundo, este tipo de energía representa aproximadamente la cuarta parte de la producción total de electricidad, y su importancia sigue en aumento. Los países en los que constituye fuente de electricidad más importante son Noruega (99 %), Zaire (97 %) y Paraguay (96 %). La central de Itaipú, en el río Paraná, está situada entre Brasil y Paraguay, se inauguró en 1982 y tiene la mayor capacidad generadora del mundo. Como referencia, la presa Grand Coulee, en Estados Unidos, genera unos 6500 MW y es una de las más grandes.
En algunos países se han instalado centrales pequeñas, con capacidad para generar entre un kilovatio y un megavatio. En muchas regiones de China, por ejemplo, estas pequeñas presas son la principal fuente de electricidad. Otras naciones en vías de desarrollo están utilizando este sistema con buenos resultados.
Ancient Rome
The ancient Romans, who spread their own model of urban life throughout the Mediterranean, based well-being and good living especially on the availability of abundant amounts of water. It is considered that aqueducts supplied more than one million m³ of water per day to Imperial Rome, most of it distributed to private homes through lead pipes. At least a dozen aqueducts connected to a vast underground network reached Rome.
To build the Claudio aqueduct, more than 40 thousand cars of tufo per year were required for 14 consecutive years.
In the Roman provinces aqueducts often crossed deep valleys, as in Nîmes, where the 175 m long Pont du Gard has a maximum height of 49 m, and in Segovia, in Spain, where the 805 m long aqueduct bridge still operates.
The Romans also dug canals to improve the drainage of rivers throughout Europe and, less frequently for navigation, as is the case of the 37 km long Rhine-Meuse canal. But without a doubt in this field the masterpiece of engineering of the Roman Empire is the drainage of Lake Fucino"), through a gallery&action=edit&redlink=1 "Gallery (geology) (not yet written)") 5.5 km below the mountain. This gallery was only surpassed in 1870 by the railway gallery of the Moncenisio. The “Portus Romanus”, completely artificial, was built after the one in Ostia, in the time of the first Roman emperors. Its internal, hexagonal bay had a depth of 4 to 5 m, a width of 800 m, a dock "Muelle (construction)") of brick and mortar "Mortar (construction)"), and a bottom of stone blocks to facilitate dredging.
Power generation
The main source of energy in ancient times was the so-called Greek “mill”, made up of a vertical wooden shaft, at the bottom of which there was a series of paddles submerged in water. This type of mill was used mainly to grind grains, the shaft passed through the lower machine and rotated the upper machine, to which it was attached. Mills of this type required a swift current, and probably originated in the hilly regions of the Middle East, although Pliny the Elder attributes the creation of watermills for grinding grain to northern Italy. These mills were generally small and rather slow, the grinding stone rotated at the same speed as the wheel, they therefore had a small grinding capacity, and their use was purely local. However, they can be considered the precursors of the water wheel, and their use spanned more than three thousand years.
The type of hydraulic mill with horizontal axis and vertical wheel began to be built in the century BC. C. by the military engineer Marco Vitruvio Pollio. Its inspiration may have been the Persian wheel or “saqíya”, a device for raising water, which was formed by a series of containers arranged on the circumference of the wheel that was rotated with human or animal force. This wheel was used in Egypt (Century BC). The Vitruvian water wheel, or wheel of cups, is basically a wheel that works in the opposite direction. Designed for grinding grain, the wheels were connected to the moving machine by means of wooden gears giving a reduction of approximately 5:1. The first mills of this type were of the type in which the water passes underneath.
Later it was observed that a wheel fed from above was more efficient, also taking advantage of the difference in weight between full and empty cups. This type of wheel, significantly more efficient, requires a considerable additional installation to ensure the water supply: generally a watercourse was dammed to form a reservoir, from which a canal carried a regularized flow of water to the wheel.
This type of mill was a greater source of energy than previously available, and not only revolutionized grain milling, but paved the way for the mechanization of many other industrial operations. A mill from Roman times of the bottom-fed type, in Venafro, with a 2 m diameter wheel could grind approximately 180 kg of grain in one hour, which corresponds to approximately 3 horsepower, in comparison, a mill powered by a donkey, or by two men could barely grind 4.5 kg of grain per hour.
Since the century AD. C. in the Roman Empire, mills of notable dimensions were installed. At Barbegal, near Arles, in 310, 16 top-fed wheels, each having a diameter of up to 2.7 m, were used to grind grain. Each of them powered two machines using wooden gears: The capacity reached three tons per hour, enough to supply the demand of a population of 80 thousand inhabitants. The population of Arles at that time did not exceed 10 thousand people, it is therefore clear that it supplied a vast area.
The water wheel
In the Middle Ages, the water wheel was widely used in Europe for a wide variety of industrial uses. The Domesday Book, the English cadastre prepared in 1086, for example, reports 5,624 water mills, all of the Vitruvian type. These mills were used to power sawmills, grain and ore mills, hammer mills for metalworking or fulling mills, to power bellows (pneumatic) for foundries, and for a variety of other applications. In this way they also had an important role in the territorial redistribution of industrial activity.
More than two dozen water wheels built by the Spanish at Larmahue are still in use to supply agricultural irrigation canals, and constitute the largest group of water mills still in use in the world. The water wheels, which operate along a four km stretch of an irrigation canal of possible pre-Hispanic origin, bear witness to the Spanish colonial contribution to agriculture in the region.
A waterwheel similar in design to those at Larmahue has been reconstructed near Córdoba "Córdoba (Spain)"), Spain, and evidence of several water mills dating from the Middle Ages has been found in the vicinity of Toledo, also in Spain.
Water wheels are on the way to disappearing, many are replaced by mechanical pumps or simply due to negligence they deteriorate and disappear. In 1988, about 80 were censused in Chile, of which to date (2016) only approximately two dozen survive in use.
Another form of energy developed in the Middle Ages was the windmill. Originally developed in Persia in the 19th century, it appears to have originated in the ancient wind-powered prayer wheels used in Central Asia. Another plausible but unproven hypothesis is that the windmill would be derived from the sails of ships. During the century these windmills were widely used in Persia, to pump water. The Persian mills were made up of two-story buildings, on the lower floor there was a horizontal wheel powered by 10 to 12 wings adapted to capture the wind, connected to a vertical axis that transmitted the movement to the machine located on the upper floor, with an arrangement reminiscent of Greek water mills. Horizontal axis windmills were developed in northern Europe around the 17th century.
Hydraulics in Arab countries
In the Middle Ages, Islam contributed significantly to the development of hydraulics. In the geographical area where the first development of the Islamic civilization is located, important hydraulic works were carried out, such as canals for the distribution of water, with frequent use of siphons, almost unknown before, but what is more significant, Islam ensured the continuity of knowledge with ancient civilizations, particularly with the Alexandrian one.
When classical civilization and its science were rediscovered in the Renaissance, in reality there were much more evolved techniques than in ancient times and much more versatile mathematical instruments, such as Arabic numerals and algebra, also of Arab origin.
Among the numerous “architects” who acted in the Renaissance, the most significant was Leonardo Da Vinci (1452-1519). Leonardo is responsible for the first version of the conservation of mass in a watercourse, in which the product between the average speed of water in a section and the area of the same section is constant, while, Leonardo always observes, the speed of water is maximum in the center of the river and minimum on the edges. In recent times, the study of turbulence has been redirected to that of dynamic systems that lead to chaos. Currently, the true nature of turbulent motion is not entirely clear, and the probabilistic approach would seem to not be a simple reflection of our ignorance, but rather would reflect the very essence of the phenomenon, as in other branches of physics.
It can be concluded that “it is easier to study the movement of infinitely distant celestial bodies than that of a stream that runs at our feet” (Galileo Galilei): “Discourse on two new sciences.”