Monocrystalline vs Polycrystalline Solar Panels
When it comes to solar panels, one of the most asked questions is which solar cell type is better: Monocrystalline or Polycrystalline?
Well, if you are looking for a detailed answer, then you came to just the right place.
In this article, we will do a full in-depth comparison between Monocrystalline and Polycrystalline solar panels including:
How are they made?
What do they look like?
How efficient are they?
How well do they react to heat?
What is their expected lifespan?
Are they recyclable?
How expensive are they?
But first, let’s see how Solar PV works
Solar Photovoltaics (PV) is the direct conversion to electric current at the junction of two substances exposed to solar energy. It occurs through a process known as the Photovoltaic Effect which cause photons to be absorbed and electron discharge. Solar energy is composed of photons which are small packets of electromagnetic energy. Materials that exhibit this photovoltaic effect are known as PV or Solar cells.
Solar cells are composed of semiconductor materials, such as silicon, used in the microelectronics industry. For solar cells, a thin semiconductor wafer is specially treated to form an electric field, positive on one side and negative on the other. When light energy strikes the solar cell, electrons are knocked loose from the atoms in the semiconductor material. If electrical conductors are attached to the positive and negative sides, forming an electrical circuit, the electrons can be captured in the form of an electric current — that is, electricity. This electricity can then be used to power a load, such as a light or a tool.
The first photovoltaic module was built by Bell Laboratories in 1954.
So, without further ado, let’s jump right into how solar panels are made.
A. Manufacture
How are Monocrystalline Solar Panels Made
In 1918, the Polish scientist Jan Czochralski discovered a brilliant method for monocrystalline silicon production and called it the Czochralski Process, and later in 1941, the first cell was constructed.
The manufacture of monocrystalline solar cells contains 8 main steps and, in this section, we will quickly go through each one of them.
Make Metallurgical Silicon
The main ingredient that makes monocrystalline solar panels is silicon also known as Silica sand, Quartzite, or SiO2.
The first step in manufacturing monocrystalline cells is to extract pure silicon from quartzite to make metallurgical silicon.
To make metallurgical silicon, special ovens are used to melt SiO2 and Carbon at temperatures of over 2,552 degrees Fahrenheit leaving behind 98% to 99% pure silicon.
Although the high purity of metallurgical silicon, it’s not pure enough to be used in PV panels.
Therefore, further purification needs to be done.
Purify Metallurgical Silicon
The next step is to purify this metallurgical silicon using the Siemens process.
First, we expose the powder of metallurgical silicon Si in a reactor with HCl at elevated temperatures resulting in SiHCl3 gas.
The gas is then cooled and liquefied for distillation.
Distillation is the process of evaporating then condensing the liquid to get rid of unwanted impurities.
For instance, you can boil seawater (salted water), then condense the vapor to get pure water, as the salt will remain at the bottom of the pot.
Using the same concept, the liquified SiHCl3 is heated then cooled to remove impurities with higher and lower boiling points such as Calcium and Aluminum.
After distillation, the liquefied SiHCl3 is moved to a different insulated reactor with a hot rod, then mixed with Hydrogen gas and vaporized again at a temperature of up to 2732 degrees Fahrenheit.
Due to the heat and the presence of H2 gas, the Cl atoms will dissolve leaving around 99.9999% pure silicon behind.
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