Experimental measurements of soiling impact on current and power output of photovoltaic panels

We have investigated the impact of three different soiling types (dust, leaf, rainfall) on the current-voltage and power-voltage characteristics of a solar panel located at different locations. The current and power losses were measured regularly for 50 days (10-day interval). The soiling ratio was calculated to be a reliable parameter for soiling impact assessment. The source of current and power losses due to soiling was rooted by measuring the transmittance loss and panel surface temperature increase, external quantum efficiency and electroluminescence spectrum recorded for the range of 950-1300 nm. The results confirm leaves as the most detrimental soling type with 38% power loss compared to dust and raindrop and the lowest loss in current density and power was related to raindrop (29%). This is confirmed by the significant decrease in the soiling ratio of the leaf-soiled panels from 0.9 to <0.1 in 50 days. Electroluminescence spectra confirm the critical impact of leaf-soiling on defect generation in the materials and a reduced photocurrent generation. Leaf could reduce the current and power of the panel from 14A to 12A and from 190W to 100W, respectively.