HOW IT'S MADE: Solar Panels
Solar panels are something that climate-conscious cities and towns have made almost abundant and popular! The energy from the sun is bountiful, and it makes sense that we have to develop methods to harness this large amount of energy. The Earth actually receives approximately twenty-five times more power from the Sun than we use in the world every day!
Solar energy’s contribution to the use of energy by us has grown significantly in the last couple of decades. However, how are solar panels made?
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The Science Behind Solar Panels
The whole basis of making solar panels is by using a super-abundant material we see on earth! Can you guess what it is? It is sand! Sand is abundant in silicon and it has to be purified to about 99.999% purity. There is a very complex purification process to do this.
If you were to look into the structure of the silicon molecule, you would see that the atoms are bound together where the electrons in the structure can’t move. Only if enough energy strikes the silicon, the electrons can move. This is how a semiconductor material works. However, when the sun strikes, the movement of the particles is random, and there is no current through the load.
So you need a driving force to ensure the unidirectional flow of electrons. Boron is often infused into pure silicon to create ‘holes’ for the particles to move towards. This makes sure some electrons would migrate into this positively charged region and fill the holes available there. Because of electron migration, the boundary of the negative side becomes mildly positively charged, whereas the positive side becomes mildly negatively charged.
Fundamental physics tells us that an electric field will form between these charges and this produces the necessary driving force to move the electrons in a particular direction.
In a practical solar cell, the top layer is very thin and abundant with electrons, whereas the bottom layer is a lot thicker. Solar cells are constructed in this particular way as it results in the generation of more current. The top thin layer also makes it easy for sunlight to penetrate through easily.
How are solar panels made?
A solar panel has several layers. One of them is a layer of cells, connected in series through copper strips and it is what you often see immediately when looking at a solar panel. Another layer is a layer of EVA sheeting on each side of the cells to protect them from dirt, humidity, vibrations, and shocks to protect these light-sensitive sheets.
Step #1: Obtaining pure silicon and making the wafers.
The procedure to purify silicon from sand involves mixing carbon with it and applying high temperatures of up to 2000°C. You would obtain a gaseous silicon compound which is then mixed with hydrogen to get highly purified polycrystalline silicon. Scientists then change the shape of these silicon ingots and turn them into silicon wafers which are exactly like how it sounds: very thin slices of silicon. The silicon wafer is the brain and heart of a photovoltaic cell.
There are two main types of solar panels existing which are thin-film and crystalline silicon panels. Crystalline silicon solar modules are very common and they look like black or blue rectangular grids having smaller square-shaped cells and they tend to be interconnected together.
There are further two types of crystalline silicon designs like monocrystalline and polycrystalline designs. Monocrystalline cells can produce higher electrical conductivity but are costlier.
Polycrystalline models have more impurities but are cheaper. You can recognize a monocrystalline solar cell as the crystal framework produces uniform blue color without any grain marks thus giving the highest efficiency levels and best purity.
There are also thin-film modules that adhere to the metal foil, plastic, or glass substrates. However, they can be fragile and sometimes flexible. This can be installed on automobiles and other devices.
Step #2: Producing the Ingots
The pure silicon rocks obtained are melted at very high temperatures to get the ingots in cylindrical shapes. The thorough melting process makes sure that all atoms are perfectly aligned in the required structure and orientation. The boron is added to give the silicon positive electrical polarity. After cooling down the ingot, the grinding and polishing processes are done. The ingots will then have flat sides.
Step #3: Constructing the Wafers
The wafers are derived by slicing the silicon ingot into extremely thin disks. This process requires the use of a wire saw for extreme precision cutting. A wafer is as thin as a piece of paper, and you should remember we’d be cutting metal to that width.
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