Solar Panel is one of the most important system components in a PV plant. The efficiency of a Solar Panel can turn the ROI tables exponentially with a positive impact. SPDs (Solar Power Developers) are most curious these days to opt for higher wattage per PV module technology so that the cost of land acquisition can be reduced with increased efficiency per square meter.
Silicon is the starting point of the photovoltaic cycle. It is obtained from sand, which consists mainly of silicon dioxide. As the second most common element in the earth's crust, it is nearly infinitely available.
Silicon is the most common semiconductor material used in solar cells, accounting for approximately 95% of the modules sold today. It is also the second most abundant substance on earth (after oxygen) and the most common semiconductor used in computer chips. A crystalline silicon cell is composed of silicon atoms that bond together to form a crystal lattice.
This grid provides an organized structure that makes the conversion of light to electricity more efficient.
Silicon solar cells now offer a combination of high efficiency, low cost, and long life. The module is expected to last over 25 years and still produce over 80% of its original output.
In a second manufacturing process, high-purity silicon forms a crystalline structure at 2,500 degrees Fahrenheit and then hardens. Next, the crystallized silicon is shaped into prisms. These columns are cut into wafer-thin slices, so-called wafers, using modern wire-cut technology. After cleaning and exhaustive final testing, monocrystalline and polycrystalline wafers form the basis for solar cell manufacturing.
In the third manufacturing step, the wafers are processed into solar cells. They form the basic elements of the resulting solar modules. The cell already meets all technical requirements for generating electricity from sunlight. When exposed to light, positive and negative charge carriers are released within the cell, causing current (direct current) to flow.
In panel production, solar cells are assembled into larger units or panels. They are framed and Weatherproof. The solar energy module is the final product and is ready to generate electricity. Sunlight is converted into electrical energy in the panel. The direct current thus generated is converted into alternating current by means of so-called inverters and supplied to the public power grid or, if necessary, directly to the house.
“During the single-crystal process, polysilicon rock is heated and melted until it becomes an incandescent liquid, then resolidifies into a single giant crystal with all atoms perfectly aligned in the desired structure and orientation.”
The magic begins by carefully stacking about 250 pounds of polysilicon rock into a quartz crucible. The only other ingredient is a silicon disk impregnated with trace amounts of boron. The addition of boron dopants ensures that the resulting crystals have a positive potential orientation. The crucible is surrounded by thick walls of insulating graphite and surrounded by a cylindrical furnace.
When the crystal-growing furnace is heated to a temperature of about 2,500 degrees Fahrenheit, the silicon it contains liquefies into a shimmering melt. Alchemy begins when a computerized monitor records the correct temperature and atmospheric conditions. A silicon seed crystal hangs from a thin cable attached to a rotating device at the top of the furnace and is slowly lowered into the melt.
The crucible starts rotating and the seed crystal starts rotating in the opposite direction. The silicon melt solidifies on the seed crystal and conforms to the crystal structure of the seed crystal. As the crystal grows, the cable and seed rise slowly and the crystal expands with a controlled diameter. As the growth runs out of silicon melt, the crucible also rises.
Approximately 3.5 days after the crucible was loaded with polysilicon: After several hours of cooling to approximately 300 degrees Fahrenheit, the furnace hood and shaft were lifted from the crucible shell to reveal a finished cylindrical crystal, the second and next ready-to-move to the manufacturing room.
First, the saw cuts off what is called the top and tail of the crystal, leaving a crystal of uniform width. Typically, a wafer ring saw draws a fine wire containing a liquid abrasive across the surface of the crystal. (Above, a machine fitted with a steel blade that looks like a giant donut cuts.) A wire saw also cuts the crystals into two-foot-long ingots. A steel holder is attached to one end of these bars for the next step.
The secured billets are placed side by side in rack storage 16 in a separate wire-cutting machine. There, a grid of wires descends over the bars and shears off four rounded segments, leaving flat sides. Result: The bar now has a square cross-section, except for the rounded corners.
The next wire saw is more complicated. Hundreds of turns of wire are wound between two cylindrical drums to form a web of parallel, closely spaced segments. As the wire is machine unwound, the ingots attached to the sides of the glass and metal holders are pushed two at a time into the wire path and cut into thin business card thicknesses. Each millimetre of the crystal makes about 2.5 wafers. Wafers are removed from their holders and loaded onto carriers or boats for transport to the next process.
See Also: How Solar Panels Are Made In India?
“At this point, wafers produce less power than river rock fragments. Wafers are the main building blocks of PV cells, but so far the only notable properties are their crystal structure and positive potential orientation. That all changes in his third multistage cell production phase of PV manufacturing.”
In the only step that requires a dedicated clean room, a series of complex chemical and thermal treatments transforms bare grey wafers into highly productive blue cells.
For example, so-called texture etching removes small layers of silicon that depend on the underlying crystal structure, revealing irregular pyramidal patterns. Pyramid surfaces that are too small to be seen by the naked eye absorb more light.
The wafers in the cartridge are then transferred to a long cylindrical oven-like chamber where phosphorus is diffused into a thin layer on the wafer surface.
Impregnation at the molecular level is a step that occurs when the wafer surface is exposed to hot phosphorous gas, giving the surface a negative potential electrical orientation. The combination of this layer and the boron-doped layer below creates a positive-negative or P/N junction. This is a key barrier to PV cell functionality.
Read More: N-type or P-type cell : What is the world mulling for?
The fast-growing, still grey cells are placed in trays and moved to a heavy vacuum chamber where they are coated with a bluish-purple silicon nitride layer on top. Coating with silicon nitride (another member of silicon-based materials) is intended to further reduce reflections in the high-energy blue end of the light spectrum. Leave the cells in their final dark colour.
The cell will now be able to optimally collect photons and generate electricity. However, it lacks a mechanism for collecting and transmitting energy. In a series of screen-printing steps, pieces of metal are printed on each side of the cell, adding pinstripe "fingers" and power rail circuitry. A functioning cell is born – all it takes is sunlight to generate electricity.
Waaree is India’s largest Solar PV module manufacturing company. Keep visiting Waaree’s website for regular technological updates regarding PV cells and module manufacturing processes.
Waaree Energies Ltd. is the flagship company of Waaree Group, founded in 1989 with headquarters in Mumbai, India. It has India's largest Solar panel manufacturing capacity of 5GWs at its plants in Surat and Umbergaon in Gujarat. Waaree Energies is amongst the top players in India in Solar Panel Manufacturing, EPC Services, Project Development, Rooftop Solutions, and Solar Water Pumps and is also an Independent Power Producer. Waaree has its presence in over 380 locations nationally and 20 countries internationally. Step on to your cleaner journey by contacting us at 18002121321 or mail us at waaree@waaree.com
