Solar energy is one of the alternative kinds of energy, based on the direct use of solar radiation for energy production in any form. Solar power is used as a renewable source of energy. Moreover, it is environmentally friendly and does not generate hazardous waste.
The first solar panels capable of converting solar energy into mechanical one were built in France at the end of XIX century. After a few years, a similar machine with a capacity of 15 horsepower was created in the U.S. With a lapse of time, this technology improved but the principle remained the same: the sun – water – vapor. However, in 1953, scientists at the National Aerospace Agency of the U.S. created new device that could directly convert the sun’s energy into electricity. The notion of the so-called photoelectric effect appeared by that time. It was a phenomenon associated with the release of electrons in a solid or liquid under the action of electromagnetic radiation. In some years after numerous experiments that failed scientists finally managed to create solar cells with an efficiency of 10-15%. Then solar panels of the modern type appeared. In 1959 they were installed on one of the first artificial satellites of the Earth, and since that first attempt all the space stations are equipped with multi-meter panels with solar panels.
Low efficiency solar cells, for example, can cover the entire Sahara desert solar cells and can be used by large scale solar power plant. However, silicon semiconductors used in producing solar cells are very expensive. The higher the efficiency is, the more expensive materials are. As a consequence, the share of solar energy nowadays is rather low. However, due to fossil fuels, the proportion of energy derived from the solar power will inevitably increase. The same change in the use of solar panels contributes to the development, aimed at the improvement of the efficiency and lowering the total cost.
One of the main advantages of solar energy is that it’s very friendly for the environment. Without doubt, silicon compounds can cause little harm to the environment, but in comparison with the effects of burning fossil fuels, such damage is a drop in the ocean. Semiconductor solar cells have a very important advantage, its durability. Consequently, the solar panels are becoming more popular in modern industry and everyday life. Few square meters of solar panels may solve all energy problems of a small village. Countries with a large number of sunny days, such as, for instance, the southern part of the U.S., Spain, India, Saudi Arabia and some others, have been already using solar power plants for a long time.
According to the data revealed by the scientists, the human race needs ten billion tons of fuel and if one calculates the number of tons of such contingencies, which are provided by the sun during the year, it will make a fantastic amount – about a hundred trillion tons. Solar panels are a great means to solve all the problems caused by the lack of energy.
The major advantage of solar panels is their relatively low cost of manufacture and simplicity of operation. It’s a necessary minimum to make the collector – a few meters of a thin tube and a bit of black paint. Another, not less important virtue, is that the collector is able to capture and convert into heat more than 90% of solar radiation. Even with the presence of a light cloud cover, its efficiency exceeds the efficiency of other types of batteries. Moreover, solar panels are cheaper and are a major source of energy nowadays, provided that only last year the world total capacity of solar power plants was over 20 GW.
Usually, the term “solar panel” means more than one association of photovoltaic cells, special semiconductor devices that can directly convert solar energy. Various devices created in order to convert solar radiation into heat and electricity are the objects of study of the scholars working in the field of solar energy production. Production of photovoltaic cells and solar panels is growing rapidly in many different directions. Solar panels come in various sizes and some of them can even occupy the roof of cars and buildings.
Most effective, in terms of energy, devices for converting solar energy into electricity are known as solar panels. The physical principle of the solar panel is in energy conversion that is based on the photoelectric effect. The photoelectric effect occurs when a solar cell is illuminated by light in the visible and near infrared regions of the spectrum (Castellano, 2010). In a solar cell of 50 micrometers thick silicon semiconductor absorbs photons and consequently, energy is converted into electrical energy. The use of concentrators of solar radiation with the multiplicity of concentration 50-100 improves efficiency from 20% to 35% (Morris, 2006). In conventional silicon cells infrared radiation is not used, while in a new element in the first transparent layer it is absorbed and converted into electricity, visible light and infrared part of the spectrum that passes through this layer and is absorbed and converted into electricity in the second layer, resulting in efficiency of 37%, which can be compared to the efficiency of modern thermal and nuclear power plants. Heterogeneity structure can be obtained by doping the same semiconductor of the various impurities or by combining different semiconductors with varying band gap that is the energy of electron detachment from the or by changing the chemical composition of the semiconductor, resulting in the appearance of the gradient of the band gap.
The conversion efficiency depends on the electrical characteristics of the inhomogeneous semiconductor structures, and optical properties of solar cells, among which the most important is the photoconductivity. Key irreversible energy losses in solar panels are related to the following factors:1) reflected solar radiation from the surface of the transducer; 2) the passage of radiation through the solar cells without absorbing it; 3) scattering by thermal lattice vibrations of the excess energy of photons; 4) recombination of photo-pair formed on the surface and in the volume of solar cells; 5) the internal resistance of the converter, and 6)certain other natural processes.
In order to reduce all types of energy losses in solar cells, a set of activities are developed and successfully implemented. They include such parameters as optimal use of semiconductors for solar energy gap, the direction of improving the properties of a semiconductor structure by its optimal doping, and built-in electric fields, the transition from homogeneous to heterogeneous and graded gap semiconductor structures, optimization of the design parameters, the use of multifunctional optical coatings that provide illumination, thermal control and protection of solar cells from cosmic radiation, development of solar cells, transparent at longer wavelengths of the solar spectrum for the edge of the fundamental absorption band, creation of cascade solar cells of specially selected by the band gap semiconductor that converts each section radiation passing through the previous stage, and so on. The significant increase in efficiency of solar cells was achieved by two-way converters sensitivity. The use of luminescent reradiating structures prior expansion of the solar spectrum into two or more spectral regions followed by the transformation of each individual section of the spectrum solar cells. Solar power plants can use different types of solar panels, but not all of them meet the complex requirements of these systems: high reliability in long-term (25-30 years) of the resource; high availability of raw materials and the ability to mass production; acceptable in terms of payback period of the cost of building the system transformation; minimum expenditure of energy and mass associated with the management system conversion and transfer of energy (space), including the orientation and stabilization of the plant as a whole; and easy maintenance. Certain practices improve the performance of solar panels, for example, through the creation of complex structures, poorly compatible with the possibility of their mass production at low cost. High performance can only be achieved if the organization is fully automated in manufacturing solar panels, for example, a tape technology, and creating a network of specialized companies developed the appropriate profile, that is, in fact, an entire industry, comparable in scale to the modern electronic industry.
Manufacture of solar panels and assembly of solar cells on automated lines provide multiple cost saving batteries. Solar cells of large size, as well as solar panels are widely used in tropical and subtropical regions with a large number of sunny days. They are especially popular in the Mediterranean countries, where they are placed on the roofs of houses. Power flux of solar radiation per square meter, excluding losses in the atmosphere, is about 1350 watts. At the same time, the power density of solar radiation in Europe in a very cloudy day, even during the day, may be less than 100 W/m ². With the most common solar panels it is possible to convert energy into electricity with an efficiency of 9% -24%, and thus the price of the battery is about 1.3 U.S. dollars per watt of rated power. Structural features of the PV panels cause performance degradation with the increasing temperature. Partial shading panel causes the output voltage drop due to the losses in an unlit cell that begins to act as a parasitic load. Thus, disadvantages can be eliminated by installing a bypass for each solar cell panel. Operating characteristics of the photovoltaic panels are used in order to achieve maximum efficiency and require the correct selection of the load resistance. In order to perform this task photovoltaic panels are not connected directly to the load and the controller PV systems are used for the optimal performance panels. As for the major competitors in the marketplace, Spain and Australia are believed to be the leading countries dealing with the production of solar panels and solar thermal energy in general.These countries actively use solar power for many facilities and beat all the competitors with a considerate number of solar thermal powerhouses.
Today, the topic of alternative energy production is extremely acute. Traditional sources are drying up rapidly and can disappear in some time. Moreover, energy resources are expensive nowadays and significantly affect economy of many countries. Thus, scientists are made to look for the new ways in order to generate energy. And one of the most promising areas is solar power. After all, the sun gives life to our planet and provides us with heat and light.