Air Mass(AM), one of the parameters that affect solar photovoltaic modules yield
image credit: The credits for the picture goes to Renewables Academy (RENAC)
- May 17, 2019 1:33 pm GMT
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There are several parameters that affect a photovoltaic (PV) module yield amount such as Irradiance, Cell Temperature, Air Mass
Many people ask about the meaning of AM(Air Mass) in the STC conditions. Air mass is ratio of the actual atmospheric mass through which solar radiation travels to the minimum possible atmospheric mass at sea level. In the following formula "hS" is the sun's height angle. where "P" is local air pressure and "P0" is air pressure at sea level.
But to be honest , it's just mathematical interpretation. AM is defined as light spectral characteristic which is in nonlinear relation to the distance light travels through atmosphere. Longer waves will be less absorbed/scattered, that's why morning/evening sky is red (AM is bigger).
So "What is AM ?"
The answer has been depicted here, Air Mass (AM) is actually the proportional distance the solar radiation must pass through when the sun is in a specific solar elevation angle, in comparison with the condition when the sun is exactly overhead (90° solar elevation angle)