3.9 Solar Parameters
Solar radiation and energy calculations require some geometric and time quantities concerning the sun position relative to the earth and any point on the earth. It is also necessary to know the relation between the local standard time and the solar time.
3.9.1 Earth's Eccentricity
It is desirable to have the distance and the earth's eccentricity in mathematical forms for simple calculations. Although a number of such forms are available of varying complexities, it is better to have simple and manageable expressions such as the one suggested by Spencer (1972), who gave the eccentricity, e, correction factor of the earth's orbit as e =1.00011 + 0.034221 cosT + 0.001280sinT
where day angle, T, in radians is given as
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