Hydropower is a source of renewable energy or alternative energy. This renewable energy exploits the transformation of gravitational potential energy, possessed by a certain mass of water at a certain elevation, in kinetic energy to overcome a certain difference in height. The mechanical energy obtained can be used directly to rotate the shaft of a turbine or in some application or machine that works using hydropower. The most common is to use this kinetic energy to generate electrical energy. In this case, we talk about hydroelectric power.
How does hydropower work?
Hydropower comes from rivers and lakes thanks to the creation of dams and forced conduits. There are several types of hydroelectric power plants: in the mountain regions, jump centers are used, which are large drop heights. In the plants of fluid water, on the other hand, large masses of river water are used that overcome small differences in height.
Water from a lake or artificial basin is transported downstream through forced pipes, thus transforming its potential energy into pressure and kinetic energy thanks to the distributor and the turbine.
Mechanical energy is transformed through the electric generator, thanks to the phenomenon of electromagnetic induction, in electricity. Hydroelectric generation and pumping stations have been established to store energy and have it available at the time of greatest demand.
In hydroelectric power plants pumped, water is pumped to the upstream tanks by the use of energy produced and not required at night. In this way during the day, when the demand for electricity is greater, additional masses of water can be provided. These water pumping systems allow energy to be stored in times of availability to be used in times of need.
In spite of the considerable advantages with respect to pollution, however, the construction of dams and large basins or artificial deposits, with the flooding of large soils, always and in any case causes a certain environmental impact that in severe cases can cause the disruption of the ecosystem of the area with great environmental damage, as happened with the great dam of Aswan in Egypt, or hydrogeological risks as happened in the disaster of Vajont.
The production of hydroelectric energy can also take place through the exploitation of waves, tides and marine currents. In this case, we talk about the energy of the tides or tidal energy.
Use of hydropower
Ther are some different ways to take advantage of hydropower.
A watermill or water mill is a mill that uses hydropower. It is a structure that uses a water wheel or water turbine to drive a mechanical process such as milling (grinding), rolling, or hammering. Such processes are needed in the production of many material goods, including flour, lumber, paper, textiles, and many metal products. These watermills may comprise gristmills, sawmills, paper mills, textile mills, hammermills, trip hammering mills, rolling mills, wire drawing mills.
One major way to classify watermills is by wheel orientation (vertical or horizontal), one powered by a vertical waterwheel through a gear mechanism, and the other equipped with a horizontal waterwheel without such a mechanism. The former type can be further divided, depending on where the water hits the wheel paddles, into undershot, overshot, breastshot and pitchback (backshot or reverse shot) waterwheel mills. Another way to classify water mills is by an essential trait about their location: tide mills use the movement of the tide; ship mills are water mills onboard (and constituting) a ship.
Hydroelectricity is the application of hydropower to generate electricity. It is the primary use of hydropower today. Hydroelectric power plants can include a reservoir (generally created by a dam) to exploit the energy of falling water, or can use the kinetic energy of water as in run-of-the-river hydroelectricity. Hydroelectric plants can vary in size from small community sized plants (micro hydro) to very large plants supplying power to a whole country. As of 2019, the five largest power stations in the world are conventional hydroelectric power stations with dams.
Hydroelectricity can also be used to store energy in the form of potential energy between two reservoirs at different heights with pumped-storage hydroelectricity. Water is pumped uphill into reservoirs during periods of low demand to be released for generation when demand is high or system generation is low.
Other forms of electricity generation with hydropower include tidal stream generators using energy from tidal power generated from oceans, rivers, and human-made canal systems to generating electricity.
Compressed air hydro
Where there is a plentiful head of water it can be made to generate compressed air directly without moving parts. In these designs, a falling column of water is purposely mixed with air bubbles generated through turbulence or a venturi pressure reducer at the high-level intake. This is allowed to fall down a shaft into a subterranean, high-roofed chamber where the now-compressed air separates from the water and becomes trapped. The height of the falling water column maintains compression of the air in the top of the chamber, while an outlet, submerged below the water level in the chamber allows water to flow back to the surface at a lower level than the intake. A separate outlet in the roof of the chamber supplies the compressed air. A facility on this principle was built on the Montreal River at Ragged Shutes near Cobalt, Ontario in 1910 and supplied 5,000 horsepower to nearby mines.
The hydroelectric basin is used to collect the waters of a river in an artificial basin. The main element of the hydroelectric basin is the dam. Thanks to the dam, it is possible to raise the altitude of the water in order to subsequently use the difference in level for the generation of electricity. In this case, hydropower is used to generate electric power.
From the basin to the power plant where the generators are located, there is a forced duct to favor the exit speed in the turbine blades. A forced conduit is a pipe that has the wide initial opening and the narrow terminal.
Hydroelectric power station
A hydroelectric plant means a series of hydraulic engineering works positioned in a certain succession, together with a series of suitable machines in order to obtain the production of electricity from hydropower. The water is transported to one or more turbines that rotate thanks to the water pressure. Each turbine is coupled to an alternator that transforms the rotation movement into electrical energy.
The exploitation of hydroelectric power and the consequent production of electric power is not constant over time. The exploitation of this energy depends on the water supply of the artificial water basin, which in turn depends on the affluent / river regime and then on the precipitation regime of the catchment area.
A practice in hydropower that is very widespread in some countries / areas is to pump water in the hydroelectric dams at night when there is surplus energy and reuse the hydroelectric energy accumulated during the day, when the demand is greater and therefore the price is greater thus obtaining a net benefit. It is a way to store electrical energy.
History of hydropower
The first in history to use hydropower were the Greeks and the Romans. Initially these two ancient civilizations used this type of renewable energy only to operate simple water mills to grind corn. Over time, the factories evolved, and the water wheels installed in them also began to use the potential energy contained in the water, that is, hydropower.
At the end of the Middle Ages, with the discoveries brought by the Arabs of North Africa, other methods of exploiting hydropower are used: the hydraulic wheels were used more and more, both for the irrigation of the fields and for the recovery of vast marshy areas. The waterwheel is still used today in the mills and for the production of electricity.
A huge technical progress occurred at the end of the 19th century. Around the beginning of the Second Industrial Revolution, the hydraulic wheel evolved to obtain the hydraulic turbine. The hydraulic turbine is a machine built by a pivoting wheel on an axis, which at first was crude and schematic, but with technological innovations, especially in the first half of the twentieth century, it became increasingly refined and functional.
The turbine improved the conversion efficiency of the potential energy of water into rotational kinetic energy applied to an axis.
Last review: March 4, 2019