Construction of Solar Panels
Solar panels contain an array of closely interconnected solar cells. Solar cells are typically semiconductor devices. Hence the share the processing, design and manufacturing techniques with commonly used semiconductor devices in the electronic equipments. This article will showcase solar panels from their construction perspective.
Prerequisites: Manufacturing of solar panels is a very delicate and brittle process. Cleanliness, orderliness and quality control are some of the stringent requirements that govern the process of fabrication of solar cells used in solar panels.
The recent advancements in technologies with respect to the semiconductor fabrication have been a boon to the solar panels manufacturing industries which can now make them available at an affordable cost and in an efficient manner.
An element named silicon (chemical symbol Si) is the fundamental raw material used in solar panels. It is the second most abundant element to be found inside the earth's crust. Silicon, which is available in abundant quantities does not pose any threat to the environment in terms of depletion due to usage as well as the processing of silicon is harmless from the environmental care perspective.
Silicon is cut into tiny disks and transformed into silicon wafers. This silicon wafer, not more than a centimeter thick are then polished carefully. They are followed by any treatment to be given in order to reduce the adverse effects that might have affected them during the slicing process.
The process of polishing makes the surface of silicon free from any outside impurities. Dopants are intentionally added in the following process. Dopants are added impurities. Dopants have certain properties induced into the silicon crystal. These are under control of the process through which the dopants are added. Dopants are materials that are added so that an alteration to the electric charge could be made in a semiconductor crystal. Different types of dopants alter composition and electrical properties of silicon in different ways. These typically include p and n types of dopants. Doping density is very less, approximately one in a million or lesser.
Metal conductors that are laid across each disk of silicon crystal help carry electric current within the solar cell and complete the circuit inside the solar panel as a whole system. Metal contacts are made in such a way that they enable the underlying solar cells inside the solar panels to be connected in either series or in parallel. Metal connectors are typically in the form of flat ribbons or thin wires. These kinds of connections between two or more solar cells are packaged tightly into modules.
Solar panels are then covered inside the sheet of glass (typically tampered glass) on to the front side, so as to be transparent to the light energy (photons) and hit the solar cells lying within. Insulation is enabled through polymer encapsulation on the rear end of the solar panels.
Solar cells used within a solar panel are of different types: monocyrstalline, polycrystalline and amorphous. Monocrystalline requires purest form of silicon. They ensure high level of efficiency for solar panels. Polycrystalline being more cost-effective is used widely commercially. This encompasses use of liquid silicon. Amorphous silicon, also known as thin layer cell is a silicon film deposited on a substrate e.g. glass.
Tweaks in construction process: The cell surfaces that are used in solar panels, when made up of pyramidal structure help in reduction of the reflection losses. This facilitates the hitting of light energy (photon bombardment) several times back and forth within the solar panels. Tandem or in some cases stacked cells are also used to enable the solar panels to respond to a wide spectrum of radiation. In this case semiconductor materials suited to be responsive for different spectral ranges are arranged on top of each other and tightly packed with a solar panel.