Experimental analysis and modeling of weather condition effects on photovoltaic systems' performance: Tehran case study

Increased reliability in grid-independent photovoltaic systems is an important factor in the prevalence and greater use of solar systems. The present study was conducted in Iran. It is one of the countries with high potential in the field of solar energy with average radiation of 5-5.5 kWh/m(2)intensity. On the other hand, due to the wide desert areas, it is important to investigate the effect of dust deposition on photovoltaic panels. An experimental study on the performance of photovoltaic panels over a 90-day period from May 25 to August 22, 2018, in Tehran, and under real conditions, to investigate the effect of dust deposition and climate change on their output power was performed. Because of its large population, political and economic conditions, Tehran has the highest importance amongst other cities in Iran. The results showed that the dirty panels produced 10% less power than the clean panels. Utilization of the data achieved from the experiment, the output power of the clean and dirty panels considering the air temperature and solar radiation is modeled using the MLR method. In order to establish the relationship between the reductions of the output power of the panel, due to the deposition of walnut dust, the soiling ratio (SR) is used. This ratio is gained by dividing the output power of the dirty panel by the output power of the clean panel to obtain a coefficient to determine the reduction of the output power of the desired photovoltaic panel in terms of air temperature and solar radiation. The coefficient earned with the correlation coefficient of 0.9 (R-2) and the error of the mean root squares 7.94 (RMSE) can well predict the loss of power output of the panel due to dust sediment on the surface of the panel. The uncertainty range of experimental results is between of 7.83% to 8.08%.