| support@alphasolar.com
How Solar Cells WorkSolar cells (also called PV cells) surround us literally everywhere – many consumer items are powered by them because of the low cost and high efficiency – wristwatches, calculators, this is not to mention their use in water pumps, communication satellites, traffic signs and many other places. The amount of the sun’s energy that reaches the surface of the earth is greater than the total amount of energy people in the world use in one year. This is despite the fact that the earth receives a very small fraction of the energy released into the solar system, and part of this energy is additionally absorbed and reflected by the atmosphere. The photoelectric effect is a basic physical process during which a solar cell transforms sunlight into electric current. Although the process of converting sunlight into electricity has been discovered back in 1839 it took over a century to understand the process and realize that the photoelectric effect was also affected by the material used and the changes happening with it at the atomic level. Depending on the wave lengths of the solar spectrum the particles of solar energy called photons contain different amounts of energy, so when photons encounter a photovoltaic cell they either pass through or are absorbed and provide energy for the generation of electricity. Once the semiconductor absorbs certain amount of sunlight electrons are dislodged from the atoms of the material and start migrating to the surface. Due to the migration of electrons each carrying a negative charge the imbalance between the front and the back surfaces of the cell is formed so voltage potential is created, providing for the flow of electricity when the two surfaces are connected through an external load. However, one photovoltaic cell cannot produce enough power so the cells are electrically connected into a weather-tight module that in turn can be a part of an array. Solar cells are produced from silicon that is also used to manufacture integrated circuits. Silicon is treated in a special way so that electrons are released when they are exposed to the sun generating an electric current. There are three types of solar cells: monocrystalline, polycrystalline and thin-film, or amorphous. Amorphous cells are used most often in small solar panels – for instance, in calculators, although they may also be used in bigger applications. Individual cells are not distinctly visible in this case as they form part of a thin film attached to a sheet of another material, typically stainless steel. Although amorphous cells in terms of efficiency are less productive than mono- and polycrystalline ones their quality is constantly improving, so the hope is very soon they will be able to offer a lot more to the potential customers; right now their big advantage is a relatively low cost. Crystalline solar cells are usually wired in series to create a solar panel: for an open-circuit voltage of 20 Volts about 36 such cells are required. Although in theory the efficiency of monocrystalline cells is higher, the practical difference in performance is almost invisible. Crystalline solar cells last longer than amorphous solar cells and they are more efficient – for the time being. For example, to have the same power output you would need a smaller surface if using crystalline solar cells than if you were using amorphous solar cells. Nevertheless, the latter remains a great option for households not ready to spend too much money on energy saving and power-production but willing to improve something in their daily life in terms of possessing an autonomous source of eco-friendly renewable energy. Article
"How Solar Cells Work" (c) AlphaSolar.com More Articles: Facts
about solar 2009 (c) AlphaSolar.com |