Solar Panels: What they are, Operation, Types, Installation, and Benefits in their use
Solar energy is the renewable source, along with wind, on which the global electricity generation sector is investing the most.
In a climate of growing distrust of fossil fuels used in power generation plants (mainly coal and natural gas) and those for the transport sector (petroleum derivatives), renewable resources are gaining more and more ground.
An increasing number of public and private entities are constantly equipping themselves with technologies such as solar panels or solar thermal collectors.
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But what are solar panels?
Solar panels are rectangular modules that transform energy from the sun into electricity.
In the following paragraphs, the procedure by which crystalline silicon panels are obtained, currently the most used technology in the solar field (dividing between poly and monocrystalline), will be explained.
The essential component of solar panels is pure silicon, an element in its natural state that is not and therefore requires a purification process to be used in the manufacture of the modules.
It is mainly derived from quartz, both from the gravelly element and the pulverized one, sand (quartzite gravel and crushed quartz, the English terms). Silicon is one of the most abundant elements in nature. Also check hyundai solar panels.
The extraction concerns the silicon dioxide (SO2), which is then inserted into an electric arc furnace. Carbon dioxide and 99% pure molten silicon come out, not yet usable for photovoltaic cell production. Further refining takes place by doping the material. With the so-called Czochralski process, from molten silicon and a mechanical procedure that includes pure silicon crystals, cylindrical ingots are manufactured and subsequently used to produce the cells that are a fundamental part of the panel.
A crystalline silicon photovoltaic cell usually has an area of about 15 x 15 cm (225 cm2). Under standard operating conditions, develops a power of 3.5-4 watts peak (assuming a voltage of 0.5 volts and a current of 8 amps).
On the market, there are photovoltaic modules made up of a set of cells, with an area that is, on average, one square meter.
By connecting several cells in series, higher voltage values are obtained, while connecting them in parallel increases the current. Typically there are 36 to 72 cells and a voltage greater than 12 V, which results in an approximate power of between 100 and 200 V per module. Multiple cells form a module. Several mechanically and electrically connected modules form a panel, a standard structure that can be anchored to the ground or a building. More panels from a string and more strings form a generator.
How do they work?
solar panels operation
But what are the physical principles related to electricity production from the sun? You have to start from the basics to understand it.
There are electric charge carriers, electrons, which are substantially divided into valence and conduction electrons in an atom. The former is “attached” to the physical nucleus of the atom, while the latter is free to move and, therefore, carries an electric charge.
Semiconductors For Solar Panel
In physics, semiconductor materials are defined as the energy difference between the valence band and the conduction band is tiny. Therefore, with a minimum but sufficient energy, the electrons can jump from one to the other, carrying an electric charge. When an electron jumps from one band to another, it leaves a hole behind it. Which, when combined with another electron, can produce an electric current.
Each semiconductor material has its minimum energy, which allows it to release electrons in the valence band. The lower the latter, the more solar energy causes the electrons in the semiconductor to move and the greater the current. Silicon is among the semiconductors with the best characteristics for this process.
In any case, the total efficiency of the cell is given by its energy balance. Since clearly, not all solar energy is directly transformed into electricity. If, for example, we take the energy from the sun equal to 100, the losses concern several factors, the most important of which are:
- 20% of the input energy serves to keep the electric field stable in the transition region
- 23% are high wavelength photons that have insufficient energy to free electrons from the valence band
- 45% are the photons with a small wavelength, 32% is excess energy that is transformed into heat
- Eventually, only 13% of the solar energy is absorbed and transformed into electricity.
Types of photovoltaic panels
Between mono and polycrystalline, the global percentage of production stands at 89%. The second type of photovoltaic module by a market extension (4%) is amorphous silicon.
Amorphous means that the silicon structure is irregular. Usually, the solar panels produced are thin-film, flexible but resistant. Therefore applicable on surfaces unsuitable to accommodate a regular photovoltaic module, such as the sail of a boat.
The cost compared to traditional technology is much lower, and large modules can be manufactured. The other side of the coin concerns the low efficiencies. The rapid light degradation of the module up to 30/40% of the average efficiency.
Other materials used for this application are cadmium telluride (1%) and copper and indium diesel (0.25%). The amorphous silicon covers the remaining 5.75% of the crystalline technology mix.
There are several generations of best solar panels in Pakistan, which are classified according to productivity and efficiency.
The first generation consists of crystalline silicon cells between 100 and 150 micrometers thick. Other characteristics concern the high quality of materials, which require a high energy requirement to be processed. Still, the cells almost reach the theoretical efficiency limit of 33%.
The second generation is that of thin films (thin-film in English). They have low energy requirements and low production costs because the temperatures reached in the manufacturing process are much lower than those of the first generation. The third generation refers to technologies not yet fully developed or present on the market. These are technologies such as multi-junction cells, concentration panels, excess heat generation to increase voltage and current, and semiconductor polymers. It is hoped that these technologies will further lower the price per kilowatt-hour, from the current $ 1/2 per hour to $ 0.2. While increasing the panel’s efficiency to 40% and lowering the manufacturing price at the same time—square meter.