Part of a series in renewal energy technologies brought by M/s Paavi Solar
Friends, going further
in the specification sheet of Solar Panel, today we are going to learn about the irradiance
curve (also known as the I-V curve). Before understanding the irradiance curve, we
should know what is irradiance. In radiometry, Irradiance is the power per unit
area of incident electro-magnetic the radiation falling on a surface and is
measured in watts/m2. In photometry irradiance is known as the amount of light energy
falling on a surface per second, weather directly or diffused on reflected and
is measured in watts/sq. mtrs. and denoted by Ee where subscript e
denote energy. Technically speaking it is the light (not heat ) of the
Sun which is incident on a solar panel. In laboratory conditions irradiance of
1000 watt/sq.mtrs is chosen as test conditions.
The relevance of irradiance
curve --
The irradiance curve depicts
the generated power by a solar PV panel under different irradiance conditions
and temperatures. In this curve plotting
of generated Current and Voltage of a Solar PV Panel is done at different irradiance levels. Isc (Short
circuit current ) and Impp are plotted on the X-axis and Vmpp and
Voc is plotted on Y-axis where Voc and Isc are the maximum voltage and current generated by a panel on no-load conditions. Hence Pmax
( Isc x Voc) watts
is the maximum power generated by a panel at a laboratory condition of 1000 watts/sq. mtrs irradiance. When The solar PV system is connected with load (ie MPPT charge controller or solar
inverter ) then the maximum current generated will be Impp at a The voltage of Vmpp and the power generated will be Impp x Voc
watts. It may be emphasized here that irradiance also depends upon the relative
angle of the Sun with respect to the plane of the Solar Panel and power generated is
maximum at 25 o C and decreases with the increase in temperature of the module of the due to the surrounding temperature. The module generated voltage is
directly proportional to the temp. of the module and temp. coefficient of the
module is -0.40%/oC ( eg. a
decrease of 12% if the module temp. increases to 30o C ie an
increase of 5o C over ideal temp. of 25o C). Moreover, every
place on earth has different irradiance.
So friends by studying
this curve we come to know about the power generating capacity of a Power Panel
at the different conditions of temperature and irradiance and help in the designing
of the PV System. -
G P BOSE
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