Right from the earliest civilisations, Sun has been worshipped as a God, as the ultimate source of light and power, as the entity that can make crops grow and can cause rain and draught as and when it wishes. Sun has been a dominant part of the life of homo sapiens.
And as the race of homo sapiens advanced with advancement in technologies and its own ever broadening outlook, sun became much more than a God. In present times the sun is the only source of energy which won’t get depleted in the coming billion years. Earth with its ever expanding population of human beings and their ever increasing energy needs has become one huge sphere that keeps gobbling up various sources of energy like coal, wood, petroleum, natural gas etc. and the glitch is… all these sources are finite and may get depleted in near future. But then what would become of the children of earth? In order to find alternatives to the non-renewable energy sources, solar energy was tested and utilised in various forms and when it started producing electricity, human beings were ecstatic. But do you know how does this energy come to us?
Photovoltaics is the keyword when we talk about solar energy. The word photovoltaic derives from the Greek word “phos” (light) and the term volt, the unit of measurement for electromotive force. Photovoltaic cells are devices constructed to capture sunlight and convert it into usable electricity. Solar panels that collect sun’s energy are basically made of numerous such photovoltaic cells.
Solar cells are made of semiconductor material, such as silicon. Semiconductors are named so because of their partial capacity to let electricity to pass through them. Since they stand somewhere between conductors and insulators, they are called semiconductors. Silicon basically is a poor conductor but the crystalline structure that it possesses, makes it a good semi conductor. The outer shell of silicon atom is only half filled with electrons, so it binds strongly with other atoms to make its outer shell full and complete. To make silicon more conductive, ‘impurities’ are added in it by combining it with other elements through a process known as ‘doping’. Doping aids the free movement of electrons. A silicon conductor has two parts, each doped with a different element. The first part is doped with phosphorus, which has five electrons in its shell. When it bonds with the silicon atom, it leaves one electron unbounded which can easily be knocked loose. And when knocked loose, it produces N-type (negative) silicon. Silicon can also be doped with boron, which only has three electrons in its shell. This produces P-type (positive) silicon, which offers holes that free electrons can then fill. When energy hits the silicon, it can knock the extra electrons in the N side free, and they will move to fill the holes in the P side. Afterward, the electrons from the N-type and P-type come together and form an electrical field. The solar cell becomes a diode, allowing electrons to move from P to N, but not the other way.
Now the energy that hits these electrons is nothing but solar energy. Sunlight is made of photons, small particles of energy that can hit the solar cell and loosen the electrons on the N side. The free electrons flow from N to P, creating an electric current as they pass. Once a continuous current is obtained, an electrical field is created. Now the only thing that needs to be done is tapping this electricity for further use. And this is done by attaching a power inverter to the solar cells. This converts the electricity running as Direct Current DC to Alternating Current AC, which can then be transmitted to homes and businesses and to places where it needs to be utilized.