How do solar panels work ?
The earth accept a lot of solar power, a hundred and seventy three thousand Terawatt (173000000000000000 W). This a huge amount of energy, so is it possible that one day the world could be completely depending on solar power? To answer this question we should understand how solar panels transform solar energy to electricity.
Solar panels are made up of small units named the solar cells, they are made of silicon which is a semi-conductor and it is very abundant on earth. In a solar cell crystalline silicon is sandwiched between two conductive layers. Each silicone atom is connected to the others by four strong covalent bonds, which keep the electrons in place, so no electric current can pass.
A silicon solar cell uses two types of layers of silicon: An n-type silicon is made by including atoms that have one more electron in their outer shell than does silicon, This will cause the presence of extra electrons. A p-type silicon is produced by adding atoms such as boron or gallium that have one less electron in their outer energy level than does silicon which cause an extra spaces for electrons, these spaces are also called holes. Electrons can move across the p/n junction, leaving a positive charge on one side and creating negative charge on the other.
Light is a flow of tiny particles called “Photons”, coming from the sun, when one of these photons hits the silicon cell with enough energy, electrons can be ejected and they leave holes. The negatively charged electrons and the location of the positively charged holes are now free to move around. But because of the electric field inside the cell, electrons can only move to the n-side, and the holes are drawn to the p-side.
When the n-type and p-type are connected using a wire, the electrons will travel in this wire, they flow through an external circuit, which create electricity. Electrons are the only moving parts in the cell and they will return back where they came from. There’s nothing used up, so solar cells can last for decades.
Each silicon cell only puts out half a volt, that’s why it takes so many modules to power an entire house.
What’s stopping us from being completely reliant on solar power?
Let’s focus on the physical and logistical challenges, the most obvious of those is that solar energy is unequally distributed across the planet, some areas are sunnier than others. It’s also inconsistent because on cloudy days and at night there is less solar power.
The efficiency of the cell itself is also a challenge because the sun could be reflected and not totally absorbed, or the moving electrons can fall back into a hole before going into the wire, so photon’s energy is lost. The most efficient solar cell today still can only convert 46 % of the sunlight to electricity.
There is over then a billion of people who don’t have access to electricity especially in developing countries. Solar energy can be the available alternative for them.