There is a high need for a cost-effective mitigation strategy to reduce energy losses due to dust deposition on PV modules. The most common practice used for cleaning PV modules today is a manual-water-based cleaning method, which also to the global water crisis. Anti-soiling coatings (ASC) is one of the most cost-effective universal solutions to mitigate dust. It is applied on the top surface of the PV module to mitigate dust deposition.

As these coatings are applied on the outer surface of the PV module, durability of these coatings become an essential factor. Among the many commercial anti-soiling coatings available in the market, we had tested 4 commercial hydrophobic anti-soiling coatings (catered to PV application) under outdoor field exposure in warm and humid climatic condition.

We saw that all coatings degraded in 3 months. We further identified the stressors which degraded anti-soiling coatings under field conditions.

The factors that degraded the ASC are listed below :

Rainfall- Frequent cleaning (manual or natural cleaning by rain) abrades the ASC, which was identified as a statistically significant stressor in both outdoor field exposure test and indoor individual stress tests. The effect of frequent cleaning on the field was more severe, as, in the real field condition, combination of stressors acted concurrently.

Acid rain- Signatures of acid rain were seen in outdoor field test samples. The laboratory acid rain/acid immersion test showed that hydrophobic coated samples became hydrophilic in 220 min of acid immersion.

Combination of UV exposure and condensation- We saw that the effect of the combination of UV exposure and condensation shows a higher rate of degradation than the individual stress test of only UV exposure and water immersion. This indicates that combination of stressors, also seen in field exposure, degrades the coatings at significantly higher rates than individual accelerated stress test. Understanding the factors that degrade ASC on field, can be used in developing a standard test sequence, which will act as a baseline for the present commercial antitisoiling coating market and will also help in the development of durable antitisoiling coatings. For more detailed information, please refer to the paper - Sonali Bhaduri, Ajeesh Alath, Sudhanshu Mallick, Narendra S Shiradkar and Anil Kottantharayil.