Humanity is striving to switch to alternative sources of electrical supply, which will help to maintain a clean environment and reduce the cost of energy production. The production of solar panels is a modern industrial method. The power supply system includes sunlight receivers, batteries, monitoring devices, inverters and other devices designed for certain functions.
The solar battery is the main element from which the accumulation and conversion of energy from the rays begins. In the modern world, for the consumer, when choosing a panel, there are many pitfalls, since the industry offers a large number of products united under one name.
Silicon solar panels
These products are popular with modern consumers. The basis of their manufacture is silicon. Its reserves in the bowels are widespread, and mining is relatively inexpensive. Silicon cells compare favorably with other batteries in sunlight.
Types of Elements
The production of silicon solar panels is carried out in the following types:
- single crystal;
- polycrystalline;
- amorphous.
The above-mentioned forms of devices differ in how silicon atoms are assembled in a crystal. The main difference between the elements is a different indicator of the efficiency of the conversion of light energy, which in the first two species is approximately at the same level and exceeds the values ββof devices made of amorphous silicon.
Today's industry offers several models of solar light traps. Their difference is what equipment is used for the production of solar cells. The role is played by manufacturing technology and a variety of initial material.
Single crystal type
These elements consist of silicone cells bonded together. By the method of the scientist Czochralski, absolutely pure silicon is produced, from which single crystals are made. The next process is the cutting of the hardened and hardened semi-finished product into plates with a thickness of 250 to 300 microns. Thin layers are saturated with a metal grid of electrodes. Despite the high cost of production, such elements are used quite widely due to the high conversion rate (17-22%).
Production of polycrystalline elements
The technology for producing solar cells from polycrystals consists in the fact that the molten silicon mass is gradually cooled. Production does not require expensive equipment, therefore, the cost of obtaining silicon is reduced. Polycrystalline solar storage devices have a lower efficiency coefficient (11-18%), unlike single-crystal ones. This is due to the fact that during cooling, the mass of silicon is saturated with tiny granular bubbles, which leads to additional refraction of the rays.
Amorphous silicon elements
Products belong to a special type, since their belonging to the silicon type comes from the name of the material used, and the production of solar cells is carried out according to the technology of film devices. The crystal in the manufacturing process gives way to silicon hydrogen or a silon, a thin layer of which covers the substrate. Batteries have the lowest value of efficiency, only up to 6%. Elements, despite a significant drawback, have a number of indisputable advantages, giving them the right to stand along with the above types:
- the absorption value of optics is two dozen times higher than that of single-crystal and polycrystalline drives;
- has a minimum layer thickness of only 1 micron;
- cloudy weather does not affect the work of converting light, unlike other types;
- due to its high bending strength, it is easily applied in difficult places.
The three types of solar converters described above are complemented by hybrid products from materials with dual properties. Such characteristics are achieved if trace elements or nanoparticles are included in amorphous silicon. The resulting material is similar to polycrystalline silicon, but compares favorably with new technical indicators.
Raw materials for the production of film-type solar cells from CdTe
The choice of material is dictated by the need to reduce manufacturing costs and improve technical performance. The most commonly used light-absorbing cadmium telluride. In the 70s of the last century, CdTe was considered the main contender for space use; in modern industry, it has found wide application in the energy of sunlight.
This material is classified as cumulative poisons, so the debate on its harmfulness does not subside. Research scientists have established the fact that the level of harmful substances entering the atmosphere is acceptable and does not harm the environment. The efficiency level is only 11%, but the cost of the converted electricity from such elements is lower by 20-30% than from silicon-type devices.
Beam storages from selenium, copper and indium
The semiconductors in the device are copper, selenium and indium, sometimes the latter can be replaced by gallium. This is due to the high demand for indium for the production of flat-panel monitors. Therefore, this option of substitution was chosen, since the materials have similar properties. But for the efficiency indicator, replacement plays a significant role, the production of a solar battery without gallium increases the efficiency of the device by 14%.
Polymer-based solar collectors
These elements belong to young technologies, as they have recently appeared on the market. Organic semiconductors absorb light to convert it into electrical energy. For production, carbon group fullerenes, polyphenylene, copper phthalocyanine, etc. are used. As a result, thin (100 nm) and flexible films are obtained, which give an efficiency coefficient of 5-7% in the work. The value is small, but the production of flexible solar panels has several positive aspects:
- large funds are not spent for manufacturing;
- the ability to install flexible batteries in places of bends, where elasticity is of primary importance;
- comparative ease and availability of installation;
- Flexible batteries are environmentally friendly.
Chemical etching during production
The most expensive in a solar cell is a multicrystalline or single crystal silicon wafer. For the maximum rational use of silicon, pseudo-square figures are cut, this same shape allows you to tightly lay the plates in the future module. After the cutting process, microscopic layers of the damaged surface remain on the surface, which are removed by etching and texturing to improve the reception of incident rays.
The surface treated in this way is a randomly arranged micropyramid, reflected from the edge of which, light enters the side surfaces of other protrusions. The texture loosening procedure reduces the reflectivity of the material by approximately 25%. In the etching process, a series of acid and alkaline treatments are used, but it is unacceptable to significantly reduce the thickness of the layer, since the plate does not withstand the following treatments.
Semiconductors in Solar Cells
Solar cell technology assumes that the core concept of solid electronics is the pn junction. If n-type electronic conductivity and p-type hole conductivity are combined in one plate, then a pn junction occurs at the point of contact. The main physical property of this definition is the ability to serve as a barrier and pass electricity in one direction. It is this effect that allows the full-fledged operation of solar cells.
As a result of phosphorus diffusion, an n-type layer is formed at the ends of the plate, which is based at the surface of the element at a depth of only 0.5 ΞΌm. The production of the solar battery provides for a shallow penetration of carriers of opposite signs that arise under the influence of light. Their path to the influence zone of the pn junction should be short, otherwise they may extinguish each other upon meeting, without generating any amount of electricity.
Using plasma chemical etching
The design of the solar battery provides a front surface with an installed grid for shooting current and the back side, which is a solid contact. During the diffusion phenomenon, an electrical circuit occurs between the two planes and is transmitted to the end.
To remove the short circuit, the equipment for solar panels is used, which makes it possible by plasma-chemical, chemical etching or by mechanical, laser means. Often used the method of plasma chemical exposure. Etching is performed simultaneously for a stack of silicon wafers stacked together. The outcome of the process depends on the duration of the treatment, the composition of the product, the size of the squares of the material, the direction of the jets of the ion stream and other factors.
Anti-reflection coating
By applying texture to the surface of the element, reflection is reduced to 11%. This means that a tenth of the rays simply reflects off the surface and does not take part in the formation of electricity. In order to reduce such losses, the front side of the element is coated with a deep penetration of light pulses that does not reflect them back. Scientists, taking into account the laws of optics, determine the composition and thickness of the layer, so the production and installation of solar panels with such a coating reduces reflection to 2%.
Contact metallization on the front side
The surface of the element is designed to absorb the largest amount of radiation, it is this requirement that determines the dimensional and technical characteristics of the applied metal mesh. Choosing the front side design, engineers solve two opposite problems. Reduction of optical losses occurs with thinner lines and their location at a great distance from one another. The production of a solar battery with increased grid sizes leads to the fact that part of the charges does not have time to reach the contact and is lost.
Therefore, scientists have standardized the value of the distance and line thickness for each metal. Too thin strips open the space on the surface of the element to absorb the rays, but do not conduct a strong current. Modern methods of applying metallization consist of screen printing. The silver paste is most justified as a material. Due to its application, the efficiency of the element rises by 15-17%.
Metallization on the back of the device
The deposition of metal on the back of the device takes place according to two schemes, each of which performs its own work. A continuous thin layer on the entire surface, except for individual holes, is sprayed with aluminum, and the holes are filled with silver-containing paste, which plays a contact role. A solid aluminum layer serves as a kind of mirror device on the back side for free charges that can be lost in dangling crystalline bonds of the lattice. With such a coating, solar panels work 2% more in power. Customer reviews say that such elements are more durable and not so much dependent on cloudy weather.
DIY solar panels
Not everyone can order and install power sources from the sun at home, since their cost today is quite high. Therefore, many craftsmen and craftsmen master the production of solar panels at home.
You can purchase photocell kits for self-assembly on the Internet at various sites. Their cost depends on the number of plates used and power. For example, small-power kits, from 63 to 76 watts with 36 plates, cost 2,350β2560 rubles. respectively. Work items rejected from production lines for any reason are also purchased here.
When choosing the type of photovoltaic converter, the fact that polycrystalline elements are more resistant to cloudy weather and work with it more efficiently than single-crystal ones, but have a shorter service life, is taken into account. Monocrystalline have a higher efficiency in sunny weather, and they will last much longer.
To organize the production of solar panels at home, you need to calculate the total load of all devices that will be powered by a future converter, and determine the power of the device. This implies the number of photocells, taking into account the angle of inclination of the panel. Some masters provide for the possibility of changing the position of the storage plane depending on the height of the solstice, and in winter - on the thickness of the snow.
Various materials are used to make the case. Most often they put aluminum or stainless corners, use plywood, chipboard, etc. The transparent part is made of organic or ordinary glass. There are photocells with already soldered conductors on sale, such are preferable to buy, since the assembly task is simplified. The plates do not stack one on top of the other - the lower ones can give microcracks. Solder and flux are applied previously. Soldering elements is more convenient by placing them immediately on the working side. At the end, the outer plates are welded to the busbars (wider conductors), after which the minus and plus are output.
After the work done, the panel is tested and sealed. Foreign masters use compounds for this, but for our craftsmen they are quite expensive. Homemade converters are sealed with silicone, and the back side is varnished based on acrylic.
In conclusion, it should be said that the reviews of the masters who made solar panels with their own hands are always positive. Once having spent the money on the manufacture and installation of the converter, the family pays for them very quickly and begins to save using free energy.