The focus on the operations and maintenance (O&M) of solar plants is as important as increasing the uptake of projects. A key aspect of solar O&M involves proper cleaning of modules to remove dust, dirt and other debris and enhance power generation. Proper cleaning can extend the lifespan of solar panels by preventing long-term damage from accumulated dirt or corrosive substances. By ensuring optimal performance, cleaning solutions help maximise the return on investment for solar installations.
This article discusses the types of cleaning solutions currently in use and also highlights advanced and upcoming methods that are currently in the research and development/pilot use stage…
Traditional, semi-automatic and automatic cleaning methods
There are broadly three types of cleaning methods currently in use – traditional wet cleaning, semi-automatic cleaning and automatic cleaning. Under traditional wet cleaning, a network of water pipes is established throughout the solar plant, with nozzles strategically placed at specific intervals for the cleaning crew to connect hosepipes as needed. After spraying water on the solar modules, a brush, mop or cloth is used for effective cleaning. Semi-automatic cleaning combines automatic rotary brushes or other cleaning methods with traditional water pipe systems. It offers a reduction in overall costs related to labour and water consumption. Meanwhile, automatic cleaning utilises a set of robotic equipment and accessories, requiring minimal manual input. The robotic system can be powered by an auxiliary power source or solar energy produced by the module itself, provided a sufficiently sized battery system is available. Implementing this method necessitates careful planning to accommodate the terrain and various execution or integration challenges.
Dipakkumar Patel, director, InSolare Energy, shares a detailed comparison of the three different cleaning methods based on different parameters. The key findings are, however, indicative and may vary based on project specifications, geography and technical considerations. According to Patel, the cleaning cycle for traditional methods takes the longest, while automatic methods are the fastest. Meanwhile, automatic methods have the lowest soiling loss (about 1 per cent), compared to traditional (2 per cent) and semi-automatic (1.5 per cent).
On the cost side, automatic methods incur high one-time capital costs and low operating costs. Meanwhile, traditional methods are the cheapest to begin with, but have high power and water requirements throughout the project lifetime as well as low efficiency. Apart from the high cost, traditional methods also come with the issue of high environmental impact due to their effect on groundwater, while automatic methods have very low impact.
While traditional and semi-automatic methods can be used on rooftop, ground and floating installations, automatic methods have limited applicability and are confined to ground installations. This is because of the complexity associated with the latter. Automatic methods face more challenges with ground contour, plot shape and commissioning, requiring more consideration for structure design and compatibility with robotic original equipment manufacturers.
Advanced and upcoming cleaning methods
Apart from these several other advanced methods are also being researched or deployed at pilot levels. These include electrostatic cleaning, hydrophobic and self-cleaning coatings, ultrasonic cleaning, deionised water with water-fed pole systems, nanotechnology-based solutions, ionised air blowers, and drone-based cleaning.
In electrostatic cleaning, electrostatic forces are used to remove dust and debris from the surface of solar panels. It is a contactless method, which helps avoid scratches on the panels. By applying an electrostatic charge, dust particles are repelled from the surface. The key advantage of this method is that it does not require water, which is preferred for arid locations and also because it avoids damage to the panel’s surface.
Researchers at the Massachusetts Institute of Technology have developed a cleaning system that uses electrostatic repulsion to remove dust particles. The particles are given a charge by an electrode and a transparent film with an opposite charge is applied to the panel. This transparent film repels the dust particles and removes them from the panel’s surface. Further, at the University of Jordan, researchers recommend the use of an electrostatic ioniser to remove dust from solar panels. This electrostatic cleaning reduces the attraction between dust particles by spraying electrostatically charged mist to neutralise the static electricity. Another upcoming dry and contactless method is the use of ionised air blowers on solar panels to remove dust. This method is planned for greater uptake in arid regions with water scarcity.
Meanwhile, hydrophobic coatings involve the use of water. Under this method, special coatings are applied on solar panels in a bid to make them water-repellent. Titanium oxide is a material often used for such coatings. When water is applied on the panel, it falls down, taking the dust and debris with it. This method often involves the use of dust repellents, which minimises the amount of dirt that sticks to the surface, in turn requiring less water for dust removal.
Another coating-based solution involves nanotechnology. These self-cleaning nano-coatings create ultra-thin layers on the panels that prevent dust from sticking on the surface. These coatings in fact also have self-cleaning properties and clean the panel when exposed to sunlight and rain. This system assists in reducing long-term maintenance needs and extends the efficiency and lifespan of the panels.
An even more advanced technique in this space is solar panels equipped with self-cleaning glasses. These glasses are coated with a material that reacts with sunlight to break down organic dirt, with rain then washing away the residue. Like any other automatic cleaning method, it reduces the need for frequent manual cleaning and water.
Another interesting method is ultrasonic cleaning, which involves the use of high frequency sound waves to remove particles on the surface of the solar panels. This can be combined with a water mist or used with only dry vibrations. As it is contactless, it ensures that no physical damage to panels.
Regarding water-based cleaning methods, an upcoming technique is to use deionised water with water-fed pole systems. Deionised water, which has no dissolved solids, can be used for cleaning solar panels, and such water leaves no residue, spots or streaks on the panels. The deionised water is sprayed on the panels from a safe distance using a water-fed pole system. Again, a key advantage of this method is that it ensures the solar panel does not incur any physical damage and is, thus, able to increase power generation. Hard water at various sites can leave mineral deposits on the panels, reducing their effectiveness. This is why the use of deionised or distilled water is often recommended.
While the use of drones for solar plant O&M is common, they are increasingly being used for cleaning purposes as well. Specialised drones are available, equipped with brushes, sprayers or air-blowing mechanisms that clean solar panels located in difficult areas. Drones are increasingly being used in remote areas for cleaning purposes apart from their usual role of identifying damage in particular panels. The use of drones is also considered safe for such locations as it eliminates the use of manual labour.
Conclusion
Net, net, the wide range and upcoming cleaning solutions for solar panels demonstrate the solar industry’s commitment to enhancing efficiency and sustainability. These solutions range from traditional wet cleaning to robotic systems and innovative technologies such as electrostatic cleaning, ultrasonic cleaning and coating-based solutions.
Each of these methods offers unique advantages and trade-offs. While automatic cleaning systems provide rapid, effective cleaning often with minimal or no water use, they often come at a higher cost. However, the efficiency enhancements these technologies bring are resulting in their rapid uptake. Traditional methods, though more labour-intensive and water-consuming, remain very popular across the country.
As the solar industry continues to grow, the development of cleaning technologies will likely focus on balancing efficiency, cost-effectiveness and environmental impact, with particular emphasis on water conservation and panel longevity. The choice of cleaning method will ultimately depend on specific project requirements, geographical conditions and the evolving landscape of solar technology.
