Solar operations and maintenance (O&M) is becoming a very important part of the overall solar power market value chain globally. Traditionally a major chunk of solar O&M was done manually. However, with the increasing scale, size, and number of solar projects in each developer’s fleet, manual O&M has become quite cumbersome. Thus, the focus is now on integrating more and more digital technology and automation to reduce the time and labor costs as well as increase efficiency. Manpower costs typically contribute 60 to 70 per cent of total O&M costs of solar power plant and this share is now slowly decreasing with uptake of more digital and automated tools.
Much of the manpower in solar O&M is used for module cleaning, inspection, and vegetation management. The shift from manual labor to automation is perhaps the most clearly visible in the case of solar panel cleaning, where the industry is witnessing a massive uptake of semi-automated and completely automated robotic solutions. This article discusses the different techniques of solar module cleaning as well as the recent innovations in this space…
Solar panels depend on sunlight falling on them to generate electricity and any impurities in the form of dust or lichen or bird droppings can interfere with this ability of solar panels. Thus, regular cleaning of these solar panels is critical for proper project performance. The frequency of solar panel cleaning and the technique used can often depend on the geography and climate of the project site.
For instance, in regions which get a lot of rain, solar panel cleaning does not need to be done very frequently, and any technique can work here depending on cost efficiency. However, in arid regions which receive very less rainfall, and which are also the most popular sites for solar installations, cleaning is required at frequent intervals. Meanwhile, these regions are also prone to droughts and have scant water resources, and thus, waterless solutions may be a more practical solution here.
The solar panel cleaning routine and technique can also be determined by the proximity of the solar project to major industrial sites or thermal power plants as well as whether they are located on rooftops or on the ground or on a water body. For instance, in very remote locations it might not be possible to do manual maintenance regularly, due to safety reasons and unavailability of manpower, and thus, automated solutions might be more suitable for such project sites.
Apart from manual spraying of water with hosepipes, tractors or even buckets, mechanical, coating, and electrostatic techniques are currently used for cleaning of solar PV panels. Mechanical techniques can be further categorised into air blowing, robotic, water blowing and ultrasonic vibration methods. All of these methods have some moving parts and require power for their operation. Further, many of these mechanical methods rely on significant volumes of water for cleaning which is a drawback in arid regions especially.
Coating and electrostatic techniques are more advanced when compared to mechanical methods of cleaning, and still significant research is being done to develop cost-efficient cleaning technologies in these two areas. Coating is basically a thin film of hydrophilic and hydrophobic nanoparticles on the solar panel surface. While hydrophobic coating makes water roll off the surface of the solar panel taking dust and other impurities along with it, the hydrophilic coating reduces deposition of dirt through a photo-catalytic reaction. Titanium oxide is a material often used for such coatings.
Coating is a beneficial method as it reduces the requirement for labor and water for cleaning. Its main benefit lies in the fact that it helps keep the panel surface clean for very long periods of time, and thus, can help in enhancing project performance. Moreover, when this technique is combined with mechanical methods, the results are more effective. However, coating as a cleaning method is still in early stages of development, and it would take some time for this to gain mass popularity. Going forward, the reliability and effectiveness of these coatings is expected to increase, and it is expected to become more cost-competitive for greater adoption.
Further, certain electrostatic techniques are also being used for cleaning solar panels. This includes the electrodynamic screen cleaning technique which uses electric curtain boards to expel dust from the solar panel’s surface. Another technique involves an induction electrostatic charge on dust particles that causes their repulsion. Like coating, these technologies need more research and development in order for them to gain greater traction.
There is significant innovation underway to develop efficient and cost-effective techniques for cleaning of solar modules. For instance, the paper “Experimental investigation of a new solar panels cleaning system using ionic wind produced by corona discharge” published in Journal of Electrostatics in July 2023 discusses the performance a solar panel cleaning device based on the ionic wind produced by corona discharge plasma.
Similarly, researchers at the Massachusetts Institute of Technology developed a cleaning system that uses electrostatic repulsion to remove dust particles that 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 surface. In another example, at the University of Jordan, researchers recommend the use of an electrostatic ionizer to remove dust from solar panels. This electrostatic cleaning reduces the attraction between dust particles by spraying electrostatically charged mist to neutralize the static electricity.
To conclude, the adoption of a particular technique for cleaning solar modules at a project site will depend primarily on the geography, climate, accessibility and most importantly the budget for technology integration. Meanwhile, the key focus for routine module cleaning at solar projects is going to be on reducing water usage and manpower deployment. Robotic module cleaning solutions have already become very popular across the globe, even in price-sensitive markets, and now waterless products are also available at competitive prices. As expected, the uptake is more in case of large utility-scale projects, where the project scale is much bigger than smaller rooftop projects and it makes more commercial sense to deploy advanced technologies here.
A key factor to consider here is the availability of skilled technicians and engineers to optimally put these advanced technologies to use. While, automation will reduce manpower requirements, skilled labor will be still be required to manage these advanced tools and ensure their effective working. Moreover, this means of upskilling of manpower to be able to address any issues that crop up while using these technologies.
It is expected that, like robotic technologies, coatings and electrostatic techniques will also start becoming popular in the years to come. Further, going forward, a combination of various cleaning techniques will be increasingly used for maximum efficiency especially as there is a greater focus on effective O&M for maximum performance of solar panels.
