Evaluation of the Best Slope Angle for a Flat-Plate Solar Collector

The performance of flat plate solar collector is affected by the value of its slope angle with respect to horizontal plane, where the variation of slope angle changes the amount of incident solar radiation. so, using the solar tracking system for solar collector will get the maximum solar radiation, the application of the solar tracking system cost has high operation and maintenance. it is usually suitable to set the solar collector at a best fixed slope angle throughout the year with less reduction in solar radiation received on the collector surface. in this work, a best slope angles were calculated for solar collectors based on the monthly mean daily solar radiations on a horizontal surface over some iraqi cities (mosul, rutba, and basra). the total of rays flux incident upon a solar collector is mainly affected by the installation angle. the solar collector can be oriented at three different angle settings. the first angle setting is to adjust the collector monthly off to give highest incident solar radiation, while the second angle setting suggests the seasonally changes (winter, spring, summer, autumn) .the final adjustment for solar collector can be achieved using the mean value for the four seasons to get yearly averaged throughout the year.