Tidal energy is due to the gravitational forces of attraction between the Moon, Earth and the Sun. Tidal energy is that which is to harness the tides, namely, the difference in average height of the seas as the relative positions of Earth and Moon, and resulting from the gravitational attraction of the latter and the sun on the water bodies of the seas.
This height difference can be exploited by interposing moving parts to the natural movement of ascent or descent of the water, with channeling and deposition mechanisms, motion for a shaft. By coupling to an alternator system can be used to generate electricity, transforming wave energy into electrical energy, a form more useful and usable energy. It is a type of clean renewable energy.
Tidal energy has the quality to be renewed, while the primary energy source is not exhausted by their exploitation, and clean, since in the energy transformation products are not produced gaseous pollutants, liquid or solid. However, the relationship between the amount of energy that can be achieved with today's media and economic and environmental cost of installing the devices for processing have prevented a remarkable proliferation of this type of energy.
Other ways to extract energy from the sea are: waves, wave energy; of the temperature difference between surface and deep ocean waters, ocean thermal gradient.
The tidal energy is converted into electricity in so-called tidal power stations, that function as a traditional dam river. The tank is filled with the tide and the water is retained until high tide to be released later through a network of narrow tubes, increasing the pressure, to the turbines that generate electricity. However, the high cost of maintaining their growth slows.
The ideal place to install a tidal power is an estuary, a bay or an estuary where seawater penetrates.
The construction of a tidal power is only possible in places with a difference of at least 5 meters between high and low tide.
Water, passing through the canal to the sea cargo, propeller drives the turbine and this, turning, drives a generator that produces electricity.
How it works
A rising tide, the dam gates are opened and water enters the reservoir.
By the reservoir's water level to its highest close the gates.
At low tide the sea level drops below the level of the reservoir.
When the difference between the reservoir and the sea reaches its maximum amplitude, the floodgates are open letting water pass through the turbines.
Low cost of raw material
No concentrated population
Available in any climate and season
Visual and structural impact on the coastal landscape
Depending on the amplitude of tides
Expensive energy transfer
Negative effect on flora and fauna
Rance tidal power plant
The Rance tidal power plant was carried out by constructing a dam that closes the mouth of the estuary and, through an airlock, This allows communication with the sea, also ensuring navigation inside. Between the walls of the artificial dam and turbines are electric generators, auxiliary engine rooms and the offices of personnel for the operation of the plant. At the top there is a way that those who travel without prior knowledge of the work not imagine the activity that takes place under your feet.
24 electrical generators powered by the same amount of water turbines, Call or double-acting reversible, rotate in both directions 5 700 rpm and achieves a maximum power of 240 MW, converting the energy of 20 000 m³ / s of salt water in the peak height. These turbines, also, function as pumps, aimed at increasing the level of water in the river-sea directions and sea-river, to increase the effectiveness of the installation.
Each machine is located inside a chamber that communicates with a steel pipe, that allows loading and unloading the sea to the reservoir and vice versa, and through another tube are allowed access by maintenance personnel. It is estimated that the cost of installation is 2,5 times that of the river hydro.