Solar panels have become an effective way of harnessing energy from the sun for domestic or industrial uses. In order to understand how a solar panel system works, it is vital to know its components. A solar cell is a semiconductor material that is made up of a large area p-n junction diode. In the presence of sunlight, it is capable of generating usable electrical energy. This conversion is important because it will create electrical energy that can be used to run applications and devices. Solar panel system cells have numerous applications. They are suited to produce energy for earth orbiting satellites, power systems and water pumping applications, among others. Photovoltaic effect was first witnessed by a French scientist called Alexandre-Edmond Becquerel. It is until the year 1883 that the first solar panel was built, however, it had only 1% efficiency. Efficiency in power producing equipment is very crucial because you cannot run heavy machinery with a device that produces low energy.
Criteria in Determining Solar Panel Efficiency
There are two main criteria used in selecting the best solar panel system – efficiency and the cost of the solar panel. Efficiency is the ratio of electric power output compared to the light power input. At noon, the sun is at its peak and solar radiation is approximately 1000 watts per meter square. The common material that is used in building cells is crystalline silicon. Crystalline silicon is classified into three categories: monocrystalline wafers, multicrystalline, and ribbon silicon. Monocrystalline wafers have an efficiency rate of up to 14%. Single crystal cells are expensive because they are cut from cylindrical ingots and they cannot cover an entire area without wastage of refined silicon. Most single crystalline solar panel systems have gaps on the corners. Multicrystalline have cast ingots and they are made from molten silicon that has been carefully cooled and solidified. These are cheaper than single crystal cells and have an average effect. On the other hand, ribbon silicon is manufactured from thin films of molten silicon and has a multicrystalline structure. These cells have low efficiency but are cost friendly and they do not require any sawing of ingots.
The current technologies in the manufacture of solar panel system depend on wafer system and in each solar panel system produced. A 300-micrometer thick panel is fabricated and soldered together to form a module. In some cases, the thin film approach is used. Here, the entire substrate is coated with a number of layers and a laser is then used to scribble and delineate individual cells. Currently, two thin film methods are used and this is amorphous silicon films and chalcogenide films.
Solar Panel System Interconnection and Modules
Solar panel system are connected electrically connected and synchronized to form modules and in this context solar panels. Solar panels have a glass sheet in front and resin encapsulated behind to keep the wafers in place from elements such as hail, rain, and wind, among others. Solar cells are interconnected in series and this mechanism is important because the voltages will add along the way. Silicon is a group 4 atom and has four valence electrons on the outer shell. Silicon atoms bonds with other silicon atoms to form strong covalent bonds. Amorphous silicon is not a long range order while crystalline atoms are arranged in ordered 3-dimensional way. Depending on the model of the solar panels, the crystalline cells or grains are arranged to give light.
According to quantum mechanics at room temperature, pure silicon is a poor conductor of electricity in that it lies in the forbidden band gap. However, silicon efficiency is improved by doping or addition of other electrons from group 3 or group 5 on the periodic table. These atoms are important in increasing the efficiency of the solar panel. Since the valence electrons will increase and there will be atoms roaming, they are free to bond with other atoms and produce a net positive effect on valence electron bonding. Silicon material that is doped with materials from group 5 in the periodic table is called P-type because they carry a positive charge. On the other hand, silicon that is doped with materials from group 3 of the periodic table is called N-type because a majority of the charge carriers are electrons and negative in nature. It is imperative to note that solar panel system with P-type and N-type are electrically neutral in that they have the same positive and negative charges.
Carriers That Generate Light
Absorption of photons creates electrons holes that are essential in diffusing electrical contacts and it could be extracted to power electrical devices. When a photon or a single light electrical light hits silicon, the photon passes through the silicon, especially when the energy of this photon is lower than the band gap. The next concept happens on solar panel system when the light that strikes the panel has a higher energy than the band gap. When this happens, energy is driven in the crystal lattice. The valence band is bound by covalent bonds and it moves far, thereby creating an energy that excites the conduction band. When the conduction band is free to move around within the semiconductor, the covalent bond that was created is crucial in initiating an electrical current transfer. When current moves through the lattice, it creates a net positive effect on current electricity creation. A photon of light is the lowest atom that light molecules can be dived into and in solar panel system, it needs to have an energy that is greater than the band gap to excite electrons on the valence to the conduction band.
A solar cell is a vast area in the semiconductor p-n junction, and the working principle is often related to the interaction between the n-type and p-type silicon molecules. In essence, the p-n junctions are made by diffusing another atom in group 5 or group 3 of the periodic table and these results in a flow of current. When an n-type and P-type electron converges, it results in diffusion and this occurs because electrons flow from a region of high electron concentration to a region of low electron concentration. When electrons flow from the n-type to p-type, region diffusion occurs and an electric field occurs. Electron type is on the n-type and they cross from one side to the other, it leaves behind a positively charged electron. In this context, the electrons fill the holes that were left behind when an electron moved from one region of the molecule to the other side. When electric field crosses from the p to the n junction, it creates a diode which allows current flow in one direction.
Carriers on the P-N Junction
Once the electron pair is created through the absorption of the photon and electron and the hole is free to move through the silicon lattice. Once this is created with a minority charge transfer, it creates an electric field that will bring about electron transfer.
Connecting To External Load
Ohmic metal semiconductor contacts both the n-type and the p-type conducts on the solar cells they are connected to an external load. Electrons are created on the n-type and then are collected at the junction and transferred to the p-type. During this process, electrons move from the n-type to the p-type where they travel through the wire and generate electricity. Solar cells are semiconductor devices that share many processing speeds and the quality of the semiconductor material is vital as it helps to determine the amount of power that is supplied to different parts of the solar panel system. Most solar panels in the modern world are made up of polycrystalline and in most cases, they are p-doped. Antireflection coatings in a solar panel are crucial because they prevent light from being reflected off the solar panel. Carrier combination is an essential aspect in that it will determine the efficiency of the solar panel. Over the past years, titanium dioxide has been utilized by many solar manufacturing companies as antireflection. It is applied to 200 nanometers and plasma enhanced chemical vapor deposition is a technique that is used in this process.
When the wafer is metalized, it reduces contact of the metal surface with other non-essential components that would otherwise cause loss of power through reflection. The rear contact surface is formed through screen printing metal paste. This is usually aluminum, and although some designs utilize other methods, the common process is sintering to make Ohmic contact with silicon material. Once the metal contacts are made, they are usually interconnected in a series manner to help add voltages, which means a higher power output. Some cells have an antireflection coating that works to increase the amount of light that is coupled into the cell. Typically, depending on the module that is being used, energy conversion efficiency will vary greatly, but most multicrystalline solar cells have an efficiency rate of up to 12%.