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Solar energy and photovoltaic cells

Solar energy is the energy associated with solar radiation and it represents the primary source of energy on Earth.
The sun is the engine of life on earth, which gives us light and heat.
Its radiation, used by plants to grow, passes in the form of chemical energy to living organisms that eat plants, and to others such as humans who feed themselves with animals and plants.
In this way we indirectly use solar energy to live.

Man managed to take advantage of this infinite energy directly through the photovoltaic cell, which generates electricity.

Thanks to particular semiconductor elements which are stimulated by light (and not by heat); the photovoltaic cell produces electricity, but how does this happen?
More than 10 years in industrial supplies sector have led JAES to become a qualified partner for some of the most important companies in the field of renewable electricity production.
The solar cell, formed by cells, converts sunlight directly into electricity by means of physical phenomenon of the photovoltaic effect, a branch of the photoelectric effect, a theory described by Albert Einstein, for which he was awarded the Nobel Prize in Physics in 1921.
The main component of the photovoltaic cell is a very common element on Earth: the silicon, which is purified and modeled in thin strips called "wafer".

If we look at the atomic structure of the silicon we can see that the valence electrons, those of the outermost layer of the atom, are linked with other silicon atoms creating a very regular crystal lattice.
As if they were pairs of pupils holding hands to form an orderly queue.

Through sophisticated technologies, atoms of different elements are inserted in the pure silicon.
This procedure is named Doping.
In this way, thanks to the presence of impurities in its crystal lattice, the silicon becomes a semiconductor;
and as you can see from our example, some children no longer have a companion/partner.

Silicon belongs to group 14 of the periodic table and has four valence electrons.
If the dopant atoms belong to elements of group 13 (therefore to three valence electrons), such as boron or gallium, a P-type semiconductor and an electron hole will be created/ obtained.
If instead elements of group 15 (with five valence electrons) as phosphorus or arsenic are used, an N-type semiconductor will be obtained and a free electron will be present in the crystalline lattice.
In a silicon solar cell, the P-type semiconductor foil is coupled to an N-type semiconductor foil;
so composing a P-N junction, the separation zone is called the "depletion region".
In this area the free electrons of the N side will fill the electron holes (=lacune) of the P side and a zone wil be created where there are no free electrons or holes.
Due to migration, the N side becomes positively charged and the P side becomes negatively charged, producing an electric field.

The outer layer of type N is much thinner than that of type P, to allow the photons to reach the depletion region, where due to the photovoltaic effect some bonds break, and electrons holes and free electrons are created.
Thanks to the strength of the electric field, they are pushed out of the junction area, generating an excess of electrons holes in the P area and an excess of electrons in the N area, thus creating a difference in electrical potential.

By connecting an external circuit to the two layers, an electron circulation is obtained, that is a direct electric current flowing from N to P and the electrons of N will fill the electrons holes in P again.

Whether it’s your house or the Bhadla Solar Park, (the largest photovoltaic system in the world), the panels must always be clean in order to maintain their efficiency.
Then, the current flow is conveyed to an inverter, which transforms the direct current into alternating current.
The latter passes through the transformer which increases the voltage of the current to be fed into the electricity grid.
Finally there is a counter to detect the amount of energy produced.

If you want to learn more about the operation of the inverter and transformer, watch our previous videos.

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