The basic unit of a solar panel is the solar cell which is made of a semi-conductor material. Silicon is the commonly used semi-conductor material to make solar cells. Atoms are added to silicon to improve its ability to generate electricity from sunlight. This is known as doping. Crystalline silicon is used to make monocrystalline and polycrystalline solar cells. Apart from crystalline solar cells, amorphous solar cells are also manufactured. Amorphous solar cell is a thin film of silicon on a sheet of steel or some other material. Here we will discuss about polycrystalline solar cells.
How is polycrystalline cell manufactured?
The polycrystalline silicon solar cells are manufactured by pouring molten silicon into a square mould and allowing it to cool and solidify. The solidified silicon cell contains many crystals because the rate of setting of the outside portion of the silicon is faster than inside portion. The presence of multiple crystals makes the surface of the cell grainy in appearance just like a gemstone. The square shaped silicon ingots are then cut into thin plates and assembled to form polycrystalline cells.
Comparison with monocrystalline panels
The efficiency of a polycrystalline panel is slightly less than that of a monocrystalline panel. The efficiency of polycrystalline solar panels can be 13-16% while monocrystalline solar panels have 15-20% efficiency. This is because the surface of a polycrystalline solar cell is imperfect and the silicon is not very pure.
A polycrystalline solar panel does not perform as well as a monocrystalline solar panel under high temperatures. This is because polycrystalline solar cells have lower heat tolerance than monocrystalline solar cells.
A polycrystalline module will produce less energy per square feet as compared to a monocrystalline module. Thus, a polycrystalline solar panel is not space efficient as a monocrystalline solar panel. This implies that more number of polycrystalline solar modules need to be installed to fulfill the energy requirements of a building, thereby making them unsuitable for small spaces.
Polycrystalline solar panels are not as efficient as monocrystalline solar panels under low lighting conditions.
The polycrystalline solar cells price is lesser as compared to the price of monocrystalline solar cells. This is because the method of manufacturing polycrystalline silicon cells is simple and costs less. The lowest cost of polycrystalline solar panels is $0.62 per watt. This is less as compared to the lowest cost of monocrystalline solar panels which is $0.75 per watt. Thus, low polycrystalline solar panel price makes it an economical choice.
The amount of silicon wasted in manufacturing polycrystalline solar cells is very less.
Polycrystalline solar panels are widely available in the market because they are easy to manufacture and the production cost is less. There is also no dearth of certified installers and repair and maintenance technicians for polycrystalline solar panels.
When to buy polycrystalline solar panels?
Polycrystalline solar panel is an environment friendly option because silicon wastage is minimal. However, there should be enough space on the roof to house many polycrystalline solar panels as less efficiency means that more panels are required to generate enough power. Polycrystalline solar panel is not suitable for houses with limited spaces but significant energy requirements. In the recent times, however, many brands have come up with polycrystalline solar panels which exhibit better efficiency and are not far behind monocrystalline solar panels in this respect. For example, polycrystalline solar panels by Conergy have a maximum efficiency of 14.13% which is not very less than 14.9% efficiency exhibited by 190W monocrystalline solar module by Sun-Earth.
Improvement in the quality of polycrystalline wafers has also helped in increasing the power ratings and efficiency of solar panels. Such polycrystalline solar panels have become popular among consumers.