Types of dirt

Dirt can consist of dust, bird droppings, leaves, and scaling.
Improper cleaning of solar panels may cause scaling accumulation on the glass, which filters solar rays and contributes to dirt build up due to roughness.
Dirt accumulated during the day absorbs moisture and dew during the night. It then dries and crystallizes on the panel in the heat of the next day and becomes more difficult to remove.
Leaving the dirt on the panels for a long period of time may give rise to lichen clinging stronger to the surface and may even damage the panel sealing.