Experimental study of dust deposition settled over tilted PV modules fixed in different directions in the southeast of Iran

Degradation of photovoltaic system's power due to dust deposition is one of the important concerns of photovoltaic investors, especially the PV modules which are installed in the hot and dry parts of a country. This issue requires to be more understood and quantify its impact on the PV module performance in installation site. This study experimentally studied the dust deposition using several glasses which were fixed in the wooden frames at different tilt angles and directions in the southeast of Iran. The dust deposition on the glasses, solar energy reduction of the dusty glasses, and PV power reduction due to dust deposition were measured in all months of the year. The results showed that the average dust deposition on the glasses is 4.6 × 10^-3 gr/m²day during the year. In case of no rain precipitation and no cleaning, this value reached 2.74 × 10^-2gr/m²day. The percentage of solar energy reduction due to dust deposition was varied between 2 and 16% during the year. A correlation for prediction of the solar energy transmittance reduction based on the settled dust on the glass samples was developed in the studied region using 1-year data collection. The average solar energy reduction was obtained 7% during the year, and this value reached 44% in case of no rain precipitation and no glass cleaning. Results showed that in the most months of the year the wind direction and the direction of the glasses with the maximum dust deposition were coincided with each other. Furthermore, the experimental measurement showed that the calculated optimum monthly tilt angle in some months of the year is not the same with the measured tilt angle due to dust deposition. The difference between the calculated and measured tilt angles in these months was 15°.