Dust is the primary cause of low solar plant performance in Indian climatic conditions. According to studies, dirty solar panels can reduce solar plant efficiency by almost 40 per cent. The dry desert areas of Rajasthan and Gujarat, which have high solar insolation, are also known for frequent sandstorms, which cause a thick layer of sand to settle on solar panels. This makes cleaning of PV modules in these regions tougher. It is estimated that a dust storm can reduce the efficiency of a solar park by up to 60 per cent.
In many arid and semi-arid regions, water can be a precious resource and due to non-availability of adequate reserves, plant operators are forced to lower the frequency of module cleaning. With this the returns from a solar plant reduce substantially. The use of robust module cleaning technologies, therefore, becomes necessary to ensure that the solar plant runs at an optimal level. But the conventional cleaning methods used in India are water intensive.
The conventional cleaning methods are labour intensive as well. And the work of operations and maintenance (O&M) engineers can be cumbersome and time-consuming at times. The engineers often clean the modules in extremely hot conditions. To avoid this, cleaning of modules is sometimes done during the early and late hours of the day. However, this solution comes with its own challenges as working at these hours is both unsafe and highly expensive.
Over the past few years, various robotic and water-free module cleaning technologies have emerged that can minimise the need for physical workforce and solve the issue of water wastage. These technologies use artificial intelligence and take into account the inclination of solar panels, geographic location, wind direction and speed to come up with the optimal cleaning solution.
Aegeus Technologies has developed one such robotic water-free module cleaning product. The product is called Unicorn and can start the cleaning process in three ways. One, sensors on the solar panels can initiate the cleaning process when the dust on the solar panels increases beyond the threshold level. This is an automatic process that does not require any human intervention. Two, the cleaning process can be initiated manually through a cloud-based remote system. The product can be switched on and off from any device by an engineer. Three, the cleaning can be scheduled daily or weekly at a predetermined time. The product also sends a notification on the remote monitoring system if the cleaning process stops due to any unforeseen reason. The notification mentions the exact module where the cleaning process has stopped. Such notifications help the O&M engineers find the reason for disruptions in the cleaning process with greater ease.
While many robotic module cleaning products have entered the solar market in India, the widespread use of such products is yet to be seen. In a price-sensitive market where O&M players have to work on thin margins, there is still greater use of cheap and manual methods of module cleaning, which are water intensive. These water-guzzling methods are still being used as there are a few challenges with robotic dry cleaning that have not been addressed completely. One, there is the issue of unavailability of spare parts. Two, robotic cleaning becomes difficult for rooftop solar installations because these products tend to be heavy. Three, a big caveat with robotic water-free cleaning is that it can only be used for cleaning dry sand. For wet sand, water-based cleaning methods are necessary. Moreover, with dry cleaning, there is the added risk of getting scratches on the PV modules.
Despite the challenges associated with robotic dry cleaning, the future outlook of this technology is positive, as work is being carried out to make these technologies widely acceptable. Start-ups like Aegeus Technologies are working closely with channel partners, project developers, O&M service providers and project developers who constantly advise on ways to improve the design and engineering of such products. Meanwhile, robotic cleaning technologies are being made lighter for their use on rooftop solar installations. To remove the risk of scratching, products are being designed in such a way as to make the interaction with the module and the brush minimal.
The development of home-grown module cleaning technologies is a big positive for the Indian solar industry, which is highly dependent on the Chinese market for even small equipment. Indian technology providers have also worked towards making these products cost competitive for the Indian market. The aim should be to persuade O&M service providers to use such technologies and to justify the higher costs with improved solar plant performance.
Based on a presentation by Suraj Vernekar, Co-Founder and Chief Executive Officer, Aegeus Technologies at a Renewable Watch conference on “O&M for Solar Plants”