All-World Solar Collector Optimum Slope Determination Basing on Site Latitude and Day Number

A rule of thumb says that a solar collector should be orientated towards Equator; is it valid all over the world? A rule of thumb says that solar collector should have a latitude tilt value; is it valid all over the world and all over the year? The present work focuses on presenting an algorithm for determining the optimum tilt angle all over the world and for any collector azimuth angle. The Earth surface, located between latitudes 66.45oS and 66.45oN, is divided into 3 characteristic zones. The first zone is the tropical between latitudes 23.45oS and 23.45oN. The second zone is the mid-latitude zone between 23.45oN and 43.45oN and between 23.45oS and 43.45oS. The third zone is the high-latitude zone between 43.45oN and 66.45oN and between 43.45oS and 66.45oS. For each of these zones an adequate method is proposed for calculating the solar collector optimum tilt. Moreover, four simple equations are proposed for predicting daily optimum tilt angle and optimum tilt angle for any number of consecutive days. The yearly possible energy gain in relation that received by a horizontal surface and latitude tilted surface is also calculated on the basis of daily optimum tilts. It is found that the above mentioned rules of thumb are not applicable for a number of consecutive days in the yea