Principle of the concentration of the solar irradiation, the Solar Thermal Power Plants

216 Views | Jan 7, 2019

Principle of the concentration of the solar irradiation, the Solar Thermal Power Plants

Solar thermal power plants: Used mainly in the United States, this system concentrates sunlight thanks to mirrors and parabolic dishes. Very high temperatures (from 400 ° C up to 1000 ° C) are then obtained and this heat will turn the water of the boiler into steam. Under pressure, it will activate the turbines that will themselves operate the alternator to produce the alternating current.

This type of plant allows, by storing this fluid in a tank, to prolong the operation of the plant several hours beyond sunset.

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The plant consists of a field of solar collectors called heliostats that concentrate the sun's rays to a fixed focus, located at the top of a tower. In cylindrical parabolic mirrors these concentrate the radiation on tubes filled with a fluid. A similar technology, Fresnel mirrors, uses flat mirrors that pivot around a horizontal axis to follow the Sun's path and thus redirect and optimally focus the sun's rays onto an absorber tube. In both technologies, the coolant (oil or molten salts), inside, is thus heated to high temperature and sent to a steam generator. The steam then rotates turbines that drive alternators producing electricity. The parabolic Dish Stirling, associating thermodynamic solar power plant and Stirling engine, makes it possible to reach very high temperatures (more than 700 ° C) and thus the greatest efficiency of all solar technologies, ie 29% compared to the 15 at 20% usual solar photovoltaic energy

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The principle of the concentration of solar irradiation has been known since Antiquity, as illustrated by the myth of Archimedes' "burning mirrors". Most often with reflective mirrors or magnifiers, a concentrating system reorients the solar radiation collected by a given surface onto a smaller target: starting a dead leaf fire with a magnifying glass uses this principle.

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