Abstract: The problem of continued power outages in Iraq which has been going on for more than 30 years is making it difficult to provide energy to BTS. The best alternative solution to providing electricity to these areas is through the use of stand-alone solar energy systems. In this study, the PSO algorithm was used for the purpose of finding the Maximum Power Point (MPP) of a proposed stand-alone solar energy system to supply power to the mobile BTS used in Iraq. Through field visits to some BTS in various mobile phone companies operating in Iraq such as Zain, Umniah and Huawei it is show that there are no alternative systems to supply electricity to these towers in the case of main power interruption except the rely on diesel generators. Some simple solar energy systems were found in these companies to charge the batteries for the outdoor BTS to ensure the continuity of electricity to the BTS but just for a few minutes until the operation of diesel generator which causes known problems such as environmental pollution and noise. The proposed system contains from solar panels, buck-boost converter and the tracking algorithm to provide power to a BTS, the system was simulated for different partial shading conditions using MATLAB 2017 a package for two systems 1560 W and 18 kW. The PSO algorithm shows good results in maximum power point tacking for the proposed stand-alone solar energy system, especially, in the case of partial shading in contrast to the P&O method which shows its failure some times to find the maximum power point. The results shows that the PSO method is better and faster than the P&O method in the case of partial shading in case of small power system (1560 W) while for large power system (18765 W) the results proved that PSO was able to reach the MPP at high accuracy but slower than in small systems in case of partial shading.