Solar energy is perhaps the most abundant form of energy that can be used to produce electricity. It is cheap, efficient and most of all renewable. You do not have to worry about solar energy getting depleted as the sun will be here with us for billions of years, if not forever. Unlike electricity generated from coal, oil or nuclear sources, solar energy does not cause any type of pollution and is therefore the most sustainable form of energy as of yet. Richard Komp, an educationist explains to us how solar panels work in his TED talk. The summary of that is given below.
However, the only way that exists today which can help us convert solar energy into electrical energy is through solar panels. Most of you must have heard of what a solar panel is. A solar panel is simply a sheet of solar cells. These solar cells are responsible for converting the energy from the sun into electricity.
As you can see, the solar panels consist of a number of solar cells that are used to produce electricity. However, when you zoom in a little bit, you will find that the real mechanism lies within these solar cells. Next, we are going to look at solar cells in more detail.
Each solar cell in a solar panel is made of silicon crystals. These silicon crystals are then made sandwiched between conductive layers that help in the flow of electricity.
What is Silicon?
In order to understand how solar cells convert solar energy into electricity, you must understand what silicon is. Silicon is a semi-conductor that is available in abundance. A silicon crystal has many silicon atoms that are bonded to one another by four strong bonds. This is because a silicon atom has four electrons in its outer most shell which means it is unstable – an atom that has an outer shell with eight electrons is the most stable. Due to this instability, the four electrons of the neighboring silicon atom is shared with the one next to it and this sharing of electrons creates the bond thus creating a structure as shown below. Therefore, a solar cell made of such silicon structures.
The P/N Junction
The P/N Junction is the factor that makes everything work. Since there are electrons being shared in a silicon crystal as shown in the previous figure, these electrons can move from their places if energy is provided. It is this energy that comes from the sun in the form of photons.
What are photons you may ask? Well, these are nothing more than light particles in sunlight. When these photons hit an electron in the silicon crystal, the electrons move through the P/N junction. A P/N junction can be considered as two layers in a silicon crystal.
In simple terms, a semi-conductor has two bands; a valence band and a conduction band. The electrons move from the valence band towards the conduction band. This creates a hole or a positive charge in the valence band and a negative charge in the conduction band. The electrons in the conduction band move forth while the holes in the valence band keep getting filled by the electrons of the neighboring silicon atoms due to the bonding mechanism explained in the previous section. When one electron moves to the conduction band, a vacancy arises in the valence band which is then filled by another neighboring electron.
This is what creates the P/N junction. The P-layer (Valence Band) has holes or positive charges while the N-Layer (Conduction Band) has electrons with negative charges.
As you may know, opposite charges attract and so the electrons that have been moved out of place by the photon from sunlight, tries to get back to the hole. However, before this can happen, the displaced electron gets conducted away by the conductive layers covering the silicon crystal. These conductive layers carry the electrons towards the electric circuit and this causes an electric flow thus creating electricity. The electrons are then pulled back toward the holes by aluminum sheets. This implies that the electron is not lost and no energy is wasted as such.
Why are not Solar Panels mainstream?
Well, there are many political, technical and physical factors that are preventing solar panels to get into the limelight. Firstly, the solar panels are quite inefficient today. The most efficient solar panel can convert only 46% of the solar energy into electricity while the commercial ones only convert 15%. The light may get reflected off the solar panel and thus not hit an electron or the photon itself might not have enough energy to dislodge an electron properly. However, large solar farms may change this as they are large plots of land filled with numerous solar panels. comment