Cell Efficiency


Consider the baby Cell as drawn here so it
has the two terminals V and I, the input is the incident solar radiation, so what is the
power input and what is the corresponding power output that this PV cell is capable
of gives you an idea of efficiency which is given by P0/P枰n now which is equal to P0
at peak power, so what is maximum power that the PV cell is capable of giving at any particular
installation is this peak power Pm. So we will call this one as Pm and this is
what is the output of the PV cell by P枰n and we know that Pm is nothing but Vm I m/Pin
now what is Pin , is that the standard insulation is one kilowatt per meter square and Pin is
given by one kilowatt per meter square into area of panel, what is the area of the panel? Go back to the data sheet, the data sheet
look at this row the sense there are 6 x 10 pieces so the poly crystalline cell between
60 cells and each cell having this area has indicated 0.156 m x 0.156 m so let us use
this in our calculation to arrive at what is power input case, so going back to the. So you see the area of the panel is 16 numbers
of the cells each having 156 mm x 156 mm area so let us convert them to meters so it is
16 x 0.156 x 0.15 6 meter square. This turns out to be 1.46 meter square so
Pin is one kilowatt per meter square into 1.46 which is 1.46 KW. Now the cell efficiency
from the data sheet is given as 16.5% before P0=Pm which is the max power will be efficiency
of the cell into Pm which is 1.46 KW x 16.5/100 which is equal to about approximately 240W. Therefore a cell efficiency I call it as efficiency
subscript cell is given by the output power delivered by the PV cell to the incident input
solar power, the output power at the peak power point is named as Pm we know that divided
by Pin, and what is a Pin? Pin is nothing but insulation which is given in kilo watt
per meter square into area of cell the total area of the cells of the cells, we shall use
the symbol L for insulation into the area of the cells which is area cell like this
and thereby therefore after substituting you see that Pm /L which is kilo watt per meter
square into the area of the cells will give you the input incident power.
Or further in terms of the peak power voltage and the currents with a Vm Vmp x Imp /L x
Acell the insulation is in kilowatt per meter square the area of the cell is in meter square,
so this is the cell efficiency however one should note that the module efficiency is
not the same as the cell efficiency, efficiency of the whole PV module actually is less than
the efficiency of the cell, what is the difference between those two? Basically it is in the
area of the cell and the area of the module now let us look at this difference. Consider a PV panel this is actually a 6 x
10 cells panel to each is a cell, this portion as I am indicating with the P mouse cursor
is a cell there are 10 such in this column and there are 6 horizontal, now if you look
at a much more closer view you will see that the cells though in the cells have some space
is between, the module is actually encapsulating all these cells there are spaces at the rim
the rim itself is occupying some area there are some spaces in between the cells.
Now all these area are not affected area and the solar insulation if even if it falls on
this area is actually not captured, therefore the entire module is actually having a bigger
area accommodating all these gaps and cases as compared to the pure cell area alone and
therefore the module efficiency is definitely going to be lower than the cell efficiency. If you come back to the datasheet and we will
look at the data sheet here you have the cell efficiency and you see the cell efficiency
is 16.5% and where are the module efficiency is actually 14.66% it is so in all types of
panels because the module area is higher than the fuel cell area and most of the time the
peak power and all these other rating the power rating as mentioned earlier here or
with respect to the Pure cell area and pure cell efficiency.
Over a practical purposes whenever you are calculating for a given application the module
efficiency is a much more conservative and better value to take because you will be using
the more practical efficiency.

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