The increasing energy demand and limited fossil fuels on one hand and the environmental and economic aspects, on the other hand, has made it essential to research in and develop the field of renewable energy and solar energy, in particular, to find a replacement energy. Solar collectors and Photovoltaic panels are the most common applications of solar energy. Because of great solar capacity, large-scale solarinstallations are usually located in very hot and dry desert areas where winds sweep dust into the air and deposit it onto the surface of solar panels and collector[1]. Whether using solar collector or photovoltaic panel, the sun radiation should pass through a cover glass before converting to heat or electricity.o thetransmission coefficientof the cover glais aimportantfor theystem efficiencyas the other factors such aanelitch (?) and orientation (?), cell temperature, maximum power point tracking and energy conversion efficiency. Settlement of dust on a glass cover causes gradual reduction of transmittance. Although how to increase the efficiency of these systems in different ways has been vastly studied and analyzed, the effect of dust accumulation on panel's and collector's efficiency has been largely ignored. To overcome this deficit, an experiment was developed in Isfahan, Iran, to investigate the factors affecting dust accumulation and their effects on the transmission coefficient of glass. The results indicate factors such as installation tilt (?), azimuth angles (?), dominant wind direction and the time in which samples are placed within the environment, are related to dust accumulation density on surface and transmittance reduction. Given that the dust fall density is strictly depended on weather conditions during the test period, unlike previous studies, in this article the transmission reduction relation instead of time is derived in terms of dust accumulation density on the surface. This equation is generalized and applicable to other regions around the world andalso different weather conditions. Up to 25% ??decline in thetransmission coefficient caused by the accumulation of dust on the surface was observed during the 70-daytest period. So to alleviate transmission coefficient droroblem,ano films ofTiO 2 andano-spraywerecoated on the glass surfaceto create self-cleaning properties. Testresultconfirmed that,these surface modifications have significant impacts in reducing transmission coefficient loss. For samples with surface modification, evewithout any rainfall,the transmission coefficient drops, sharply reduced and ithe present ofthe rain, transmissioloss reduced from 22% to 0.5% and dust accumulation problem on the surface almost completely disappears. Keywords: Solar energy, Photovoltaic system, Solar collector, Dust accumulation, Transmission coefficient , Titanium di oxide, Nano-spray, Surface modification