Article,
Solar position algorithm for solar radiation applications
Solar Energy, 76 (5): 577 - 589 (2004)
DOI: DOI: 10.1016/j.solener.2003.12.003
Abstract
There have been many published articles describing solar position
algorithms for solar radiation applications. The best uncertainty
achieved in most of these articles is greater than ±0.01° in calculating
the solar zenith and azimuth angles. For some, the algorithm is valid
for a limited number of years varying from 15 years to a hundred
years. This report is a step by step procedure for implementing an
algorithm to calculate the solar zenith and azimuth angles in the
period from the year -2000 to 6000, with uncertainties of ±0.0003°.
The algorithm is described in a book written by Jean Meeus in 1998.
This report is written in a step by step format to simplify the complicated
steps described in the book, with a focus on the sun instead of the
planets and stars in general. It also introduces some changes to
accommodate for solar radiation applications. The changes include
changing the direction of measuring azimuth angles to be measured
from north and eastward instead of being measured from south and
eastward, and the direction of measuring the observer's geographical
longitude to be measured as positive eastward from Greenwich meridian
instead of negative. This report also includes the calculation of
incidence angle for a surface that is tilted to any horizontal and
vertical angle, as described by Iqbals in 1983.
