Just like any engine would work better if it is well maintained and serviced, a solar panel can work with much greater efficiency when it is well cleaned and maintained. Solar panel maintenance is essential, because dust accumulation can degrade its performance, which can further impact the amount of power generated by the panel. A well-maintained mechanism for the operations and maintenance (O&M) of solar plants is critical to any solar power project, because it has to be undertaken throughout the plant’s life.
Cleaning solutions are one of the most important components of the O&M of a solar farm. A research paper titled “An Experimental Study on the Effect of Dust on Power Loss in Solar Photovoltaic Module” by Athar Hussain, Ankit Batra and Rupendra Pachauri has concluded that the accumulation of dust reduces the efficiency of solar modules and panels in terms of power by up to 60 per cent. Enough literature is available demonstrating the relation between cleanliness and the power efficiency of modules. As a result, cleaning solar modules is a critical process to consider whenever a solar project is undertaken.
The frequency and technique of module cleaning varies across project sites. Modules located in areas with regular rainfall may only need to be cleaned once or twice a month. However, modules in areas with high levels of pollution might require frequent cleaning. It is even more difficult for solar farms located in arid and semi-arid regions, where the water scarcity problem is pervasive due to natural conditions. As such, the water consumption levels for cleaning purposes at solar plants significantly add to their operating costs.
Cleaning mechanisms
Back when the number of panels used to be low, the majority of power plant owners relied on hiring people for manual cleaning. However, as the solar power industry expanded, the number of panels per plant grew significantly. Now, such plants are located not only on land but on waterbodies as well. When these power plants are built on land, manual cleaning is still possible, though difficult because of the increased labour costs and the challenges of working on big solar farms located in remote areas with varying weather conditions.
Moreover, plants are now being built on even seas, making the O&M process even more difficult to perform manually. Further, it has been found that solar plants installed on waterbodies face difficulties due to the accumulation of sea salt on their surfaces. Sea salt can significantly impact a panel’s power output efficiency, as it can corrode the aluminium strips used to encase the panels. Hence, removing sea salt from a panel’s surface is just as important as removing dirt.
Since solar power is now being deployed across vastly different geographies with different kinds of solar plant installations, different kinds of cleaning solutions have also emerged. The traditional method of removing dirt is to wash or wipe it away. Under this method, a simple cloth may be used to clean the surface of PV panels, with water. This technique involves frequent and repetitive procedures, and can be extremely time-consuming. A second method is semi-automatic cleaning, which makes use of both robots and manual labour. In semi-automatic systems, robots are manually moved from one row to another, or from one table to another. These systems are best suited for solar panels installed on uneven ground, as well as those that are not properly aligned or in continuity. The third method requires no manual intervention, and is expected to dominate the market in the near future. To this end, in 2019, the Ministry of New and Renewable Energy issued a
letter recommending that solar power projects be cleaned with effective usage of water, through the deployment of robotic cleaning systems. It also recommended the deployment of anti-soiling coating technologies to ease the cleaning mechanism.
Emerging technologies
With the rise in demand for smart cleaning solutions, a number of new products are emerging, enabled by time and cost saving technological developments. In November 2022, Delhi-based Greenleap Robotics Private Limited officially launched the Lotus A4000. It is a fully autonomous, waterless panel cleaning robot. It uses ultra-soft microfibre cleaning fins with combined airflow, and can control its impact to remove dust particles without damaging a panel’s anti-reflective coating. It can also be used to remove bird droppings. The company promises an 80 to 90 per cent reduction in bird droppings across four cleaning cycles. The robot is powered by an onboard lithium battery and can complete a single cleaning cycle of a 1 MWp solar plant in less than 2.5 hours. The battery takes less than two hours to charge fully.
Moreover, new innovations can help combine the operations of cleaning and remote monitoring across a solar plant. For instance, in March 2022, Belgian clean-tech start-up ART Robotics revealed a fully automated solar panel cleaning service consisting of autonomous cleaning robots placed on solar panels using drones. The product, named “Helios”, features two parts, the cleaning bot and the drone. The first is a small robot that can clean solar panels on its own. It has a traction system that enables it to move on inclined surfaces, and even cross over to adjacent panels. Using accurate position estimation and edge detection, the robot can navigate autonomously. Its brush and vacuum combination provides a thorough cleaning of the panel surface. The Helios drone places the cleaning robots on the solar panels and retrieves them once cleaning is completed. The deployment process is also autonomous, though it is monitored, in case something goes wrong.
Recent developments
In October 2022, the Avaada Group signed a long-term contract with Israel-based Airtouch Solar for the maintenance of its solar modules using robotic cleaning solutions. The agreement is for a period of 25 years. It includes the supply, erection, testing, commissioning, O&M of Airtouch robotic cleaning systems at Avaada’s solar farms. As part of this agreement, Airtouch will be using its robotic solutions to dryclean the solar modules at its Bhadla plant in Rajasthan and at Pangaon and Damangaon in Maharashtra. Additionally, in September 2022, Airtouch Solar signed an agreement with ReNew Power for the supply, installation, O&M of solar panel-cleaning robots for several projects.
These smart solutions are not just limited to large-scale industrial solar farms, but are being applied in the rooftop solar space as well. In May 2022, Skilancer Solar, an India-based clean-tech firm, announced the release of an automated waterless robot for cleaning small-scale solar power plants on household rooftops.
Outlook
The precious natural resource of water is already limited, and is being overused by the increasing population. Thus, it is extremely important to devise technologies that do not waste it. For solar energy to be purely sustainable, it is crucial to address the water usage of solar plants. As reported by the Solar Energy Industries Association, water usage by solar power plants depends on the technology and climate conditions at the site. In general, all solar power technologies use a decent amount of water, amounting to approximately 20 gallons per MWh for the cleaning of solar collection and reflection surfaces such as mirrors, heliostats and PV panels. This means that a very high volume of water will be required for India’s planned solar deployments. This needs to be minimised, because clean energy must ensure optimal usage of other valuable resources.
The government can play a significant role in promoting the use of efficient cleaning technologies, as well as encouraging research and development towards the local production of robotic and automated solutions. This can be done by incentivising the domestic production of such technologies. Drycleaning solutions using artificial intelligence-backed systems can pave the way for waterless cleaning.
Going forward, it is important for developers to incorporate these solutions in their ecosystems, as they will help save not only O&M costs but also precious water resources.
By Nikita Choubey
