Figure 3
From: Effects of soiling on photovoltaic (PV) modules in the Atacama Desert

The red curves show the power output of the four PV modules (two clean and two soiled) of our system in Iquique. The blue curve shows the Soiling Ratio (SR) taken in this case as being equal to the ratio between the power output of the soiled modules and the power output of the clean control modules. (a) Measurements on January 3rd, 2018 (clear sky conditions). (b) Measurements on November 6th, 2017 (overcast conditions).