Why Doesn’t Rainwater Clean Solar Panels?

Why Doesn’t Rainwater Clean Solar Panels?

Solar panel owners often think that rainwater is enough to keep them clean. However, this is like assuming that rainwater can keep your car or home windows clean. Rainwater is not sufficient to remove dirt as well as other issues such as bird droppings, dead insects, pollen, and pollution. Rainwater typically lacks the necessary pressure to remove layers of dirt, such as bird droppings or buildup from the rain. Just like in window cleaning, both rainwater and tap water can leave stains. This is due to the particles present in the water. When rainwater evaporates, it leaves behind dust particles on the surface. These particles vary depending on the location of the solar plant. For example, in industrial zones, rain is more likely to contain acid rain. After dry seasons, the rain brings down dust particles from the air, which then stick to the panel surface, leaving stains.

Furthermore, the loose dust on the panel surface, combined with rain, causes dust to accumulate under each solar panel, leading to significant heating. This buildup can cause the panel surface temperature to rise, from 41°C–45°C to 71.3°C in the accumulation area. Bird droppings or other materials that stick to the surface with rainwater, if left uncleaned, can oxidize and lead to hotspot formation.

When one photovoltaic cell on a panel is shaded, it forces current through the other cells, causing them to heat up. This can significantly reduce the energy output of your panels and shorten their lifespan. Worse yet, it may lead to hotspot formation, rendering your panels unusable. Hotspot formation can even cause fires on your solar panels. In thermal images, we can observe the temperature rising to 80°C due to the accumulation of loose dust particles carried by rainwater.

To prevent issues like hotspot formation and pollution-related losses, solar panels must be cleaned properly. This requires the use of a purified water system. Purified water can be obtained using a deionization (DI) unit or a reverse osmosis/deionization (RODI) unit.

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