The history of solar panels
It so happened historically that solar panels are the second attempt of mankind to harness the unlimited energy of the Sun and make it work for its own good. The first to appear are solar collectors (solar thermal power plants), in which electricity is generated by water heated to a boiling point under concentrated sunlight.
Solar panels generate electricity directly, which is much more efficient. With direct transformation, much less energy is lost than with multistage, like in collectors (concentration of sunlight, heating of water and steam generation, rotation of a steam turbine and only at the end the generation of electricity by a generator).
Modern solar cells consist of a chain of photovoltaic cells – semiconductor devices that convert solar energy directly into electrical current. The process of converting energy from the sun into electrical current is called the photoelectric effect.
The French physicist Alexander Edmond Becquerel in the middle of the 19th century discovered this phenomenon. The Russian scientist Alexander Stoletov created the first active photocell half a century later. And already in the twentieth century, the photoelectric effect was quantitatively described by Albert Einstein, which does not require presentation.
Principle of operation
Either a semiconductor is a material in which atoms have extra electrons (n-type), or vice versa, they are not enough (p-type). Accordingly, a semiconductor photocell consists of two layers with different conductivity. An n-layer is used as a cathode, and a p-layer is used as an anode.
Excess electrons from the n-layer can leave their atoms, while the p-layer captures these electrons. It is the rays of light that “knock out” electrons from the atoms of the n-layer, after which they fly into the p-layer to occupy empty places. In this way, electrons run in a circle, leaving the p-layer, passing through the load (in this case, the battery) and returning to the n-layer.
The first photovoltaic material in history was selenium. It was with its help that photocells were produced in the late 19th and early 20th centuries. But given the extremely low efficiency (less than 1 percent), they immediately began to look for a replacement for selenium.
Mass production of solar cells became possible after the telecommunications company Bell Telephone developed a silicon-based solar cell. It is still the most widely used material in solar cell manufacturing. True, the purification of silicon is an extremely costly process, and therefore, little by little, alternatives are being tried: compounds of copper, indium, gallium and cadmium.
It is clear that the power of individual photocells is not enough to power powerful electrical appliances. Therefore, they are combined into an electrical circuit, thereby forming a solar battery (also called a solar panel).
The photocells are attached to the frame of the solar battery in such a way that they can be replaced one at a time in case of failure. To protect against external factors, the entire structure is covered with durable plastic or tempered glass.
Solar panels are classified according to the power generated by electricity, which depends on the area of the panel and its design. The power of the sun’s rays at the equator reaches 1 kW, while in our area in cloudy weather it can drop below 100 W. As an example, we will take the average indicator (500 W) and in further calculations we will build on it.
Amorphous, photochemical and organic solar cells have the lowest coefficient of photoelectric conversion. In the first two types, it is equal to about 10 percent, while in the latter it is only 5 percent. This means that with a solar flux of 500 watts, a solar panel with an area of one square meter will generate 50 and 25 watts of electricity, respectively.
In contrast to the aforementioned types of solar cells, solar cells based on silicon semiconductors are used. The coefficient of photoelectric conversion is at the level of 20%, and under favorable conditions – and 25% for them as usual. As a result, the power of a meter solar panel can reach 125W.
The global leaders in solar cell manufacturing are Suntech, Yingli, Trina Solar, First Solar and Sharp Solar. The first three represent China, the fourth – the United States, and the fifth, as you might guess, is a division of the Japanese corporation Sharp.
The American company FIRST SOLAR not only produces solar panels, but also takes direct participation in the design and construction of solar power plants. The most powerful SES Agua-Kalient in the world, which is located in Arizona, USA – the work of the original SOLAR engineers.
The largest Ukrainian SES “PERovo” built and supplied the Austrian company Activ Solar with sun panels.
The Chinese company Suntech became famous for preparing for the summer Olympiad-2008 football stadium called “Bird’s nest” in Beijing. Electricity produced throughout the day with solar cells is accumulated, and then used to illuminate the stadium, watering herbs on the football field and the operation of telecommunication equipment.
Two more decades ago, the circle seemed to the micro calculators with photocells, which made it possible to change the “battery-tablet” in them for years. Now mobile phones with a built-in back cover are not surprised by a solar panel. But this is a trifle in comparison with cars and aircraft (albeit unmanned), who have learned to move with the help of alone solar energy. The future of solar batteries seems exactly the same light as the sun itself. I want to believe that it is solar batteries that finally cure smartphones and tablets from “compensation”.
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