I was looking into Perez model as implemented in SSC in cmod_pvwattsv0.cpp and comparing it to the technical handbook.
According to the module and other resources, the airmass should be
Attachment eq-am0.png not found
where b is the incidence angle.
Somehow in
this line
the equation for airmass is:
AIRMASS = 1.0 / (CZ + 0.15 * pow(93.9 - ZENITH, -1.253) );
and CZ in
this line
is:
CZ = cos(zen);
where zen is the sun's zenith in radiations and ZENITH the sun's zenith in degrees.
Shouldn't the equation for airmass replace CZ with cos(inc)? or am I missing something?
Thanks in advance.
Best,
Mustafa Alotbah