Solar Panel:
Solar panel is a device that converts sunlight into electrical energy. It plays an important role in
Renewable energy as it is a clean and sustainable source of energy. It is made by silicon
semiconductor cell. When sunlight hits semiconductor silicon the energy from it is absorbed and
converted into moving electorns. These electrons move through the material which give us our
useful electrical energy.
Type of Cell:
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P-type:
A solar panel is made of many solar cells attached together the cell itself is made of silicon
which is dopped with another material. There are two types of PV cells and the key difference
between both types are doping. In P-type they are dopped with Boron which contains lesser
electrons than silicon making the cell positively charged.
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N-Type:
N Type cell are dropped with phosphorus which contains more electrons than silicon thus making
the cell negatively charged.
As the first applications of solar panel were in space missions, P- Type panels were widely
produced and available in market due to its resistance against radiation but with boron doping
comes oxygen based defects when used in atmosphere where oxygen is abundant, boron can
react with oxygen causing defects or impurities in cell and lowering overall efficiency of panel
this effect is called light induced degradation for this reason lately the market has primarily
shifted towards N-type panels which degrade much slowly.
Types of Panels
As PV cells are grouped together they form a PV Panel, PV panel may be further classified by its
crystalline structure or on number of PV absorbing faces.
Mono Crystalline:
Mono crystalline panels are made by single silicon crystal pressed into a cell. They are made of
high quality silicon, as the entire cell is cut from a single crystal they contain very little
impurities due to which they have higher efficiency compared to poly crystalline and are more
expensive.
Poly Crystalline:
Poly crystalline panel is made by melting smaller silicon crystal fragments and cutting a wafer
from end product. Due to this they tend to be less efficient than mono panels as melting and
moulding small crystals into a wafer can introduce impurities or resistance to electron flow. They
are cheaper than mono crystalline as the material required is cheaper and process is simpler.
Mono-facial Panels:
Mono- Facial panels can be either mono- crystalline or poly crystalline but they absorbs sunlight
only by front side which faces the sun, most of the panels available in market are mono facial
which can be recognized by the back side being coated. These panels are designed to get
maximum gain only from the side facing the sun and due to this their installation is simpler and
targets maximum area coverage
Bifacial Panels:
Most of Bifacial Panels are made from mono crystalline cells and as the name suggests have both
sides of the panel capable of absorbing solar energy. Most of the energy gained is from front side
but bifacial panels are capable of generating higher power by absorbing sunlight from the back.
Sunlight may enter and pass through the cell and be reflected by a reflective surface on ground
back onto the panel or the sunlight traveling at extreme angles may be reflected by ground back
onto panel.
This increased energy is called the bifacial gain. Due to panel requiring reflective
surface behind panel to get its full benefit bifacial panels require a more planned and specific
installation requiring panels to at a certain tilt, height and requiring the treatment of roof surface
with reflective material as well as repeated maintenance of roof. Bifacial panel are also more
expensive than mono facial thus their selection should be considered on case basis.
