Glancing at a solar panel, with its sleek and shiny black surface, many people might assume that the cells are made of glass or some other similar material. However, the individual cells on a solar panel are actually made up of silicone crystals. If you’re surprised by this, you’re not alone. Keep reading to learn more about where the silicone used in solar panels comes from, and how it’s turned into an energy-producing power cell.
Extraction of Silica
Silicone comes from silica, which is a compound found in sand, quartz and other various minerals. Silica-rich sand deposits are mined through techniques like open-pit mining or dredging. Once the silica-rich sand is extracted, it undergoes processing to remove any impurities and separate the silica from the other minerals present in the sand.
Conversion to Silicon
There are many different processes that can be used to convert silica to silicon. The most common method is called the Siemens process. This is a highly scientific process, and it would take several books to give a full explanation of how the conversion is done. However, the simplest breakdown of the method involves mixing silica with carbon in the form of coke or coal. The mixture is then heated in an electric arc furnace at extremely high temperatures (around 3,632 degrees Fahrenheit).
This produces metallurgical-grade silicon, known as MGS, which is close to 99% pure. The MGS retrieved from the Siemens process still contains impurities like aluminum, iron, and other elements, so it’s not quite ready for your solar panels yet.
Refinement to Polysilicon
To produce the high-purity silicon solar cells needed, MGS goes through further purification to become polysilicon, which is over 99.999% pure silicon. The purification process involves several complex steps, including a chemical treatment, zone refining, and chemical vapor deposition. The polysilicon is then processed into various forms that are suitable for solar panel manufacturing.
Final Silicone Production
Finally, the polysilicon is further processed to produce silicones, which are polymers with repeating units of silicon and oxygen, often combined with organic compounds. Depending on whether you are producing a mono PV module or poly PV module, either a single silicon crystal or the fragments of several crystals can then be used to create a solar power cell. Utilizing a single crystal usually results in a much more efficient energy panel, making monocrystalline PV modules the preferred option for most solar installers.
