Filosofia

Solar Panels
The photovoltaic panels are composed of numerous cells that convert light into electricity. The cells are sometimes called photovoltaic cells, the Greek "photos" light. These cells depend on the photovoltaic effect by the light energy that produces positive and negative charges coming from two different semiconductor type, thereby producing an electric field capable of generating acurrent.
Crystalline silicon and gallium arsenide are typical choice of materials for solar cells. The gallium arsenide crystals are created especially for photovoltaic use, while crystals are available silicon ingots produced mainly cheaper standard for consumption microelectronics industry. The polycrystalline silicon has a lower conversion efficiency, but also lower cost.
When exposed tosunlight, a silicon cell of 6 cm in diameter can produce a current of about 0.5 amperes at 0.5 volts (equal to an average of 90 W / m², usually in a range of 50 - 150 W / m², depending on the solar brightness and efficiency of the cell). Gallium arsenide is more efficient than the silicon, but also more expensive.
Silicon cells most commonly employed in the photovoltaic panels can be divided intothree categories:
• monocrystalline silicon cells are constituted by a single crystal silicon. This cell type has a dark blue uniform.
• polycrystalline silicon cells (also called multicrystalline) are constituted by a set of silicon crystals, which explains that their yield is somewhat lower than monocrystalline cells. They are characterized by a more intense blue.
• Amorphous silicon cells. Theyare less efficient than crystalline silicon cells but also less expensive. This type of cell is, for example, which is used in solar applications such as watches and calculators.
The crystalline ingots are sliced ​​into thin discs as a wafer, polished to eliminate any damage caused by the cut. Introducing dopants (impurities added to modify the conductive properties) within the wafer, and metalconductors are deposited on each surface: a fine mesh on the side where sunlight gives a flat sheet and is usually at the other. Solar panels are built with these cells properly cut. To protect the front surface damage caused by radiation or by the use of these is the link on a cover glass and are anchored on a substrate (which may be a rigid panel or blanket soft). Electrical connections are madein series-parallel to determine the total output voltage. The foundation and the substrate must be thermally conductive, since the cells are heated by absorbing infrared energy that is not converted into electricity. Since the heating of the cells reduces the efficiency of operation it is desirable to minimize it. The resulting assemblies are called solar panels or solar groups.

There are twotypes of solar panels:
• Solar thermal panels: solar thermal collectors called, convert light into heat. There are two types of thermal solar panels: water traps and air.
In the collectors of water, the water flowing through the tubes provided with fins. For best performance, the assembly is placed in a box of insulating glass since this is achieved with a greenhouse effect. With good sun, andif the hot water needs are moderate, a simple network may be sufficient. The fins, which form what is called the absorber, are heated by solar radiation and transmit their heat to the water flowing through the pipes. Water collectors are used for heating and / or domestic hot water.
In the air manifolds, the air is circulated and heated in contact with the absorbent. The hot air is then vented soon heating environments used in sheds or for drying of agricultural products.
• Photovoltaic solar panels: photovoltaic modules, convert light into electricity.
In both cases, the panels are generally flat, with width and several meters in length. They are designed for easy installation and the price is fixed so that they can be used for both domestic and industrial applications.

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