Analysis of irradiance losses on a soiled photovoltaic panel using contours

• An irradiance loss factor to quantify relationship between irradiance, tilt angle and power of soiled panel is proposed.
• Artificial soiling experiment and Sieve analysis are performed to obtain data for developing contours.
• Contour analysis is used to observe the deviation in power of a soiled panel from clean panel.
• A correction factor to calculate power of a soiled panel is proposed.
• The correction factor is expressed in terms of soil particle size composition present on panel.

This paper introduces an irradiance loss factor that quantifies the relationship between irradiance, tilt angle and power output of a soiled panel with the soil particle size composition. Artificial soiling experiments were performed using four soil samples at irradiance levels between 200 and 1200 W/m2 at 18 tilt angles. Biharmonic interpolation was used to develop power contours in terms of irradiance and tilt angle from experimentally obtained data. These contours were compared with ideal ones of a clean panel to observe deviation in the nature of contours for a soiled panel. A correction factor in terms of particle size composition (as a coefficient to tilt angle) was proposed to calculate power output of a tilted soiled panel. The angular loss on a panel with soil sample containing 150 μm particle size in abundance was observed to be 22% and for sample containing 75 μm particles in majority, the loss is 24%. Presence of 300 μm particle size in abundance causes a 23.7% loss, while 52% angular loss was observed for soil with highest composition of less than 75 μm particle size.

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