Energy supply has been a very important issue for human societies since ancient times. In today's era, due to the industrial and technological advances that have a very important place in the daily life of people, the importance of the problem is manifested in a more obvious way. But the common sources of energy production, which are mostly non-renewable, will be exhausted by the end of the 21st century, according to scientists' research. Therefore, in the last decades of the 20th century, renewable energy sources received special attention. Among other reasons for paying attention to new sources of energy was the destructive effects of non-renewable sources (fossil fuels, etc.) on the environment. According to the above reasons, scientists turned to new and renewable sources of energy in order to discover new ways. It should be noted that renewable energies are directly or indirectly derived from the sun's energy, and they can be used under the name of solar energy, and their distinctive feature is that they are unlimited. It is reminded that the process of generating energy from wind or waves is somehow related to the existence of the sun and the heating energy of the lower levels of the earth is also the same. The important thing here is that today's technologies must be able to use solar energy. Therefore, it should be possible to convert solar energy (renewable sources) into the types of energy used, or that the technologies have the ability to produce the required energy from the sun. One of the suitable ways to use renewable energy sources is the photovoltaic system. This system is based on the direct conversion of solar energy into electrical energy. Solar power systems (photovoltaic) have been used after the World War and are used in all spaceships and artificial satellites to provide electrical energy.
The cost of building the above systems was very expensive in the beginning, but over time, by using appropriate production methods and increasing the efficiency of solar power systems and reducing production costs and increasing the price of fossil fuels, these systems were able to take their place more and more among other forms of energy supply. open in the world and today it is widely used in the countries of Western Europe, Latin America and the deserts of the continent of Africa and Asia (Middle East) and other deserts of the world.
In western countries with less than two percent of the sun hours of the Middle Eastern countries, people use solar power systems connected to the power grid, deliver the produced electricity to the grid during the day and receive it from the grid at night, and when paying The price of consumed electricity is the difference between delivered and consumed electricity from the grid. It is possible to use photovoltaic cells to supply the required energy as follows:
1- Use independently from the power grid;
2- Use connected to the power grid.
Since the earth contains 27.7% silicon, it is both potential and cheap, but converting silicon to solar cells is a costly process.
History
The knowledge of solar energy and its use for various purposes goes back to our time before history, at that time, the priests of the temples polished with the help of large golden cups and the sun's rays were used to light the hearths of the altar. or during the era of the pharaohs of Egypt in the years 1419-1455 due to the sun shining on the talking statues, the air inside them was warm and the statues made a sound. Of course, the most important story related to the use of the sun is the story of Archimedes, the great scientist and inventor of ancient Greece, who set the Roman fleet on fire using the thermal energy of the sun. It is said that Archimedes, by installing a large number of small square mirrors next to each other on a movable base, focused the sun's rays on the Roman ships from a distance and thus set them on fire. For this reason, Archimedes is called as the founder of using solar radiation, while the Egyptian sources are older than that.
About 1800 years after Archimedes, a person named Kercher (1610-1680) repeated the feat of Archimedes and using a number of mirrors, he set fire to an anchorage and proved that the story was true. In 1615, Salmon from France published a statement about the solar engine. Using a number of lenses installed in a frame, he focused the sun's rays on a closed metal cylinder that was partially filled with water. Sunlight heats the air inside the cylinder, and as the air expands, the pressure inside the chamber increases and water is pushed out. In the 18th century, Natura built the first solar furnace in France. His largest furnace consisted of 360 small flat mirrors, each of which independently focused the sun's rays to a single point. This researcher also designed and produced a smaller furnace consisting of 168 pieces of mirrors in 1747, with which he fired a log of wood at a distance of 60 meters.
Solar cooking devices were first built by Nicholas Day in 1799-1740. The oven consisted of an insulated box with a black plate. It was made up of glass parts of the cover. The sun's rays entered the box by passing through the glass and was absorbed by the black surface and increased the temperature inside the box to 88 degrees Celsius.
Anthony Lavazier 1743-1794, the creator of modern chemistry, in order to obtain the most energy from the purest heat source, conducted research on solar furnaces and built a furnace that formed a convex lens of this furnace from two lenses. He used a glass filled with alcohol between these two plates. The liquid lens had a diameter of 130 cm and a focal length of 320 cm. Because the refractive power of this liquid lens was not effective to obtain a high temperature at its center, this device was able to melt even platinum at a temperature of 1760 degrees.
In 1813, the father of Foulad Jahan provided the heat required for his furnace by using solar energy. In the 19th century, efforts were made to convert solar energy into other forms of energy such as steam production and use in steam engines. In these years, several solar steam engines were built and tested.
Research related to photovoltaic technology also began a hundred years ago. In his experiments, he came to the conclusion that selenium's ability to conduct electricity has a direct relationship with the amount of light emitted to it. In 1878, Mushu designed the first solar collector with a cone-shaped concentrator. The mirrors inside the cone focused all the solar rays at a point in the middle of the incomplete cone where an absorber was installed. This collector was called Oxycon. The first large oxycon that was made consisted of a silver plate with a diameter of 540 cm and an area of ??18.2 square meters. Its weight with all moving parts was about 1400 kg and it had the power to absorb 78% of the radiated solar energy. . In 1880, "Charles Fritz" was able to make a solar electric cell using selenium, and after that in the same year, the first solar flat collector was made by Charles Tellier. In the 19th century, solar water desalination devices became popular and devices were built that were able to produce about 20,000 liters of distilled water on sunny days. Photovoltaic products also produced electricity without consuming raw materials and without producing heat and noise. This research lasted until 1905. When "Albert Einstein" presented his theory about the photovoltaic effect, it remained stagnant. Einstein's theories created a revolution in the stages of electricity production, but due to high costs and low production efficiency, slow progress was made in this field. Until in the early 1950s, during their research on remote communication systems and the discovery of new sources of energy, Bell Lab scientists realized the sensitivity of silicon, the second most abundant element on earth, to sunlight and realized that when this material is used with a certain impurity, it produces energy with a significant voltage in the face of light radiation. In 1954 They produced the first silicon solar cell with an efficiency of 60% and this technology was used for the first time in a rural telecommunication station in the state of Georgia.