To obtain maximum energy from the irradiance, the PV module must always be facing the sun.
In northern hemisphere the modules will be positioned facing due south.
Theoretically the module should be tilted equal to the latitude of the site location.
However in practice, in the latitude from 0 to 15 deg, the module will generally be tilted at 10 degree to the horizontal.
Solar irradiation reaching the top of the atmosphere is called solar constant Gc=1367 W/m^2
Solar irradiation at sea level on earth is 1000 W/m^2
Daily irradiation is commonly referred as peak sun hour (PSH). The number of PSH for the day is the number of hours for which energy at the rate of 1000 W/m^2 would give an equivalent amount of energy to the total energy for that day.
Unit for PSH is (kWh/m^2)/(kW/m^2) or hour.
The energy in SI unit is Joule. To convert M/J^2 to peak sun hour, use the following formula:
Air mass (AM) is the path length the sun's array has to travel through the atmosphere to reach earth surface.
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