Page 268 - Applied Photovoltaics
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Appendix
B
EQUATIONS FOR
CALCULATING SUN
POSITION
Definitions
AZI = solar azimuth (0–360q)
ALT = solar altitude (elevation), relative to horizontal (zenith = 90q)
ZEN = zenith angle, relative to vertical = 90° – ALT
ORI = orientation of surface normal relative to azimuth
HSA = horizontal shadow angle
VSA = vertical shadow angle on perpendicular normal plane
INC = angle of incidence relative to surface normal
LAT = geographical latitude of site (negative for South)
DEC = declination (between sun-earth line and equatorial plane)
HRA = hour angle from solar noon (15° per hour)
SRA = sunrise azimuth (i.e. azimuth at sunrise)
SRT = sunrise time
NDY = number of day of year
N = day angle
TIL = tilt angle of surface relative to horizontal
