Solar energy usage in Iraq is facing many issues; one of those is the accumulation “of the dust on the surface of the solar module which” would highly lower its efficiency. The present work study the effect of dust accumulation” on installing fixed solar modules with different inclined angles 15o, 33o, 45o, 60o. Evaluation of the solar modules performance under different circumstance conditions such as rain, wind and humidity are considered in study of dust effect on solar module performance. The results show that the lowest output average efficiencies of solar modules occurs at 15o horizontally inclined angle are 7.4% , 6.7% , 8.0% , 8.1%, and 8.4% for the corresponding months; June, July, August, October, and September respectively while the highest average efficiencies are 8.9% , 9.1% , 9.4% , 9.6% , 9.6% for an inclined angle 60o for the same month. lose power output rate for angle 15o horizontally inclined solar modules are as following 32.6%, 32%,31.6%,34.9%,26.2% for months; June, July, August, October, and September respectively , while the results for the 60o horizontally inclined solar module are 26.9%, 17%, 24.2%, 28.1%, and 9.7% for the same five months. As a final result is that the 15o horizontally inclined solar panel is less efficient compared with the 60o horizontally inclined solar panel and the difference in the results in the months was mainly due to the weather changes (summer and winter). The solar modules efficiency and lose power rate values for the inclination angles 33o and 45o are ranged between the values of 15oand 60o inclination angles.
