Solar power utilizes photons from sunlight and creates electricity. Also termed photovoltaics, solar cells most commonly utilize ultra purified silicon as a semiconducting material. When light strikes a solar cell some of the energy is absorbed and transferred to the semiconductor. Electrons are freed and create an electric current that is collected through contacts on the top and bottom of the solar cell.
A photovoltaic, or PV, system is primarily comprised of solar modules electrically connected in series. The solar module is manufactured through a series of processes beginning with the purification of the semiconducting material silicon, ingot growth, wafer slicing, cell construction, and module encapsulation. A detailed description of the solar module processing steps is detailed below.
POLYSILICON
Polysilicon is an essential raw material in the production of PV cells. Polysilicon is created by refining quartz or sand through a series of steps that result in rods or chunks consisting of extremely pure silicon crystals. Click here to go to Polysilicon FAQ.
SILICON INGOTS AND WAFERS
Before polysilicon rods or chunks can be used in solar cells, they must first be converted into ingots, which are cut into wafers. There are two processes for making ingots from polysilicon: the monocrystalline and the multicrystalline process. To make monocrystalline ingots, a single crystal of polysilicon is grown, whereas, multicrystalline ingots are made by melting chunks of polysilicon together in a crucible to form a large block of multicrystalline polysilicon, which is then cut into smaller bricks. The monocrystalline ingot or the multicrystalline brick is then cut into thin wafers, typically using a cable saw. The end product is either a monocrystalline or a multicrystalline silicon wafer.
SOLAR CELLS
Solar cells are made from silicon wafers. The wafer undergoes a process to combine positive and negative layers on the wafer, attach electrodes, and coat with anti-reflective materials. The performance of a solar cell is measured by its solar radiation conversion efficiency. The solar radiation conversion efficiency is a measure of the net percentage of energy from solar radiation that the solar cell converts into electricity. Solar cells made from multicrystalline wafers may have efficiencies in the range of 13-18%, whereas solar cells made from monocrystalline wafers typically have higher efficiencies in the range of 20%, but are more expensive to produce.
SOLAR MODULES
Solar modules are commonly known as solar panels. A solar module is made by electrically wiring together solar cells in series to increase the total voltage output. The connected cells are laminated in a glass or plastic covering and then framed. The wires connecting the solar cells terminate in a junction box to allow multiple solar modules to be electrically connected in series to further increase the voltage and power output.
PHOTOVOLTAIC SYSTEMS
A photovoltaic system consists of one or more solar modules electrically connected in series, and typically includes a power inverter to convert the direct current, or DC, electricity produced by the modules into alternative current, or AC, electricity that is required for most applications.
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