How Solar Panel Works?

Solar panels are devices that consist of solar cells that convert light into electricity. They are called solar or sun or "sol" because the sun is the strongest light source that can be utilized. Solar panels are often called photovoltaic cells, photovoltaic can be interpreted as "electric light". Solar cells rely on the photovoltaic effect to absorb energy. In general, a solar cell is a semiconductor that can absorb photons from sunlight and convert it into electricity. The solar cells are made of very small pieces of silicon coated with special chemicals to form the basis of solar cells. Solar cells generally have a minimum thickness of 0.3 mm made from sliced ​​semiconductor material with positive and negative poles. In solar cells, there is a connection (function) between two thin layers made of semiconductor material, each of which is known as a "P" (positive) type semiconductor and an "N" (negative) type semiconductor. Type P silicon is a surface layer that is made so thin that sunlight can penetrate directly to the junction. Part P is given a ring-shaped nickel layer, as a positive output terminal. Under the P section, there is a type N section coated with nickel as well as a negative output terminal.

A semiconductor is an element with electrical capability between a conductor and an insulator. (Albert Paul Malvino, 2003: 35). The solar cell is a device that has the ability to convert sunlight energy into electrical energy by following the photovoltaic principle, the existence of energy from light (photons) at certain wavelengths will excite a portion of electrons in a material to the energy band found by Alexandre Edmond Becquerel (Belgium) in 1894. This effect can arise mainly in electric semiconductors which have medium conductivity due to the nature of electrons in separate material in certain energy bands called conduction bands and valence bands. The two energy bands respectively from the lower energy are the valence band and the conduction band, while the state without electrons is called the bandgap. This bandgap is of different magnitude for each semiconductor material but is required not to exceed 3 or 4 eV (1 eV = 1.60 x 10-19 J).

The process of converting or converting sunlight to electricity is possible because the materials that make up solar cells are semiconductors. More precisely it is composed of two types of semiconductors, namely, type n and type p. The type n semiconductor is a semiconductor that has an excess of electrons, so the excess charge is negative, (n = negative). While the p-type semiconductor has excess holes, so it is called p (p = positive) because of the positive overload. Initially, the manufacture of these two types of semiconductors was intended to increase the level of conductivity or the ability of electric conductivity and heat of natural semiconductors. In this natural semiconductor, electrons and holes have the same amount. Excess electrons or holes can increase the electrical conductivity and heat of a semiconductor. These two types of n and p semiconductors, when combined together, will form p-n or p-n diode connections. Another term calls it metallurgical junction which can be described as follows.

Shortly after these two types of semiconductors are connected, there is a transfer of electrons from semiconductor n to semiconductor p, and hole transfer from p semiconductor to semiconductor n. The electrons of the semiconductor n are united with holes in the p semiconductor which results in the number of holes in the semiconductor p decreasing. This area has finally become more negatively charged. At the same time. holes of the p semiconductor unite with electrons in the semiconductor n which results in the reduced number of electrons in this region. This area is finally more positively charged.

 These negative and positive regions are called depletion regions marked with the letter W. Both electrons and holes in the depletion region are called minority charge carriers because they exist in different types of semiconductors. Due to differences in positive and negative charges in the depletion region, an internal electric field E emerges from the positive side to the negative side, which tries to pull holes back into the p semiconductor and electrons to the semiconductor n. This electric field tends to oppose the movement of holes and electrons at the beginning of the depletion region. The existence of an electric field causes the pn connection to be at the equilibrium point, ie when the number of holes that move from the semiconductor p to n is compensated by the number of holes drawn back toward the semiconductor p due to the electric field E. Similarly, the number of electrons that moves from semiconductor n to p is compensated by the flow of electrons back to semiconductor n due to the attraction of the electric field E.

The solar radiation constant of 1353 W / m2 has reduced its intensity by absorption and reflection by the atmosphere before it reaches the earth's surface. Ozone in the atmosphere absorbs radiation with short wavelengths (ultraviolet) while carbon dioxide and water vapor absorb part of the radiation with longer wavelengths (infrared). In addition to the direct reduction in the earth's radiation or spotlight by absorption, there is still radiation scattered by molecules of gas, dust, and water vapor in the atmosphere before reaching the earth which is referred to as radiation spread.

The amount of daily radiation received by the earth's surface is shown in Figure 2.10. In the morning and evening, the radiation that reaches the earth's surface is of low intensity. This is due to the direction of sunlight not perpendicular to the surface of the earth (forming a certain angle) so that the sun's rays experience diffusion events by the Earth's atmosphere.

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