Solar Panels

Solar panels make use of renewable energy from the sun. They are a clean and environmentally sound means of collecting solar energy. Solar panel is a photovoltaic module or photovoltaic panel which is a packaged interconnected assembly of photovoltaic cells, also known as solar cells. The photovoltaic module, known more commonly as the solar panel, is then used as a component in a larger photovoltaic system to offer electricity for commercial and residential applications. Because a single photovoltaic module can only produce a certain amount of wattage, installations intended to produce larger electrical power capacity require an installation of several modules or panels and this is known as a photovoltaic array. You've probably seen calculators that have solar cells, calculators that never need batteries, and in some cases don't even have an off button. As long as you have enough light, they seem to work forever. You may have seen larger solar panels on emergency road signs or call boxes, on buoys, even in parking lots to power lights. Although these larger panels aren't as common as solar powered calculators, they're out there, and not that hard to spot. There are solar cell arrays on satellites where they are used to power the electrical systems.

Photovoltaic cells are made of special materials called semiconductors such as silicon, , when light strikes the cell, a portion of it is absorbed. This means that the energy of the light goes to the semiconductor. This energy knocks electrons loose, allowing them to flow freely. PV cells have electric fields that force electrons freed by the absorbed light to flow in a specific direction. This flow i­s a current which can be used externally. Pure silicon is a poor conductor of electricity because electrons are not free to move about. A solar cell has silicon with impurities . These impurities have a purpose. Consider silicon with an atom of phosphorous here and there, maybe one for every million silicon atoms. Phosphorous has five electrons in its outer shell, not four. It still bonds with its silicon neighbor atoms , the phosphorous has one electron that is left alone . It doesn't form part of a bond, but there is a positive proton in the phosphorous nucleus holding it in place. When energy is added to pure silicon, for example in the form of heat, it can cause a few electrons to break free of their bonds and leave their atoms. A hole is left behind . These electrons then move freely around the crystalline lattice looking for another hole . These electrons are called free carriers, and can carry electrical current. There are so few of them in pure silicon, however, that they aren't very useful. Our impure silicon with phosphorous atoms mixed in is a different story. It turns out that it takes a lot less energy to knock loose one of our "extra" phosphorous electrons as a result, most of these electrons do break free, and we have a lot more free carriers as compared to pure silicon. This process of adding impurities is called doping. This process is the base for the working of a photovoltaic cell which forms a solar panel.

Solar Panels