Solar operations and maintenance (O&M) is becoming an increasingly crucial part of the solar power market value chain in India and globally. Traditionally, a significant portion of solar O&M was performed manually. However, with the growing 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 time and labour costs as well as to increase efficiency. Manpower costs typically contribute 60-70 per cent to the total O&M costs of solar power plants and this share is now slowly decreasing with the uptake of more digital and automated tools.
Much of the manpower in solar O&M is used for tasks such as module cleaning, inspection and vegetation management. The shift from manual labour to automation is perhaps the most evident in the case of solar panel cleaning, where the industry is witnessing a massive uptake of semi-automated and fully automated robotic solutions. This article discusses the different techniques of solar module cleaning as well as the recent innovations in this space.
Solar panels rely on sunlight to generate electricity and any impurities, such as dust, lichen, or bird droppings, can hinder their ability to catch sunlight efficiently. Thus, regularly cleaning these solar panels is critical for proper project performance. The frequency of solar panel cleaning and the technique used can typically depend on the geography and climate of the project site.
For instance, in regions with heavy rain, the need for solar panel cleaning is reduced, and various techniques can be deployed based on cost efficiency. However, in arid regions that receive very little rainfall, and which are also the most popular sites for solar installations, cleaning is required at frequent intervals. These regions are also prone to droughts and have scant water resources, and thus waterless solutions may be a more practical solution.
The solar panel cleaning routine and technique can also be determined by factors such as the proximity of the solar project to major industrial sites or thermal power plants, as well as whether they are installed on rooftops, on the ground, or on a water body. For instance, in very remote locations, it might not be possible to carry out regular manual maintenance due to safety reasons and the unavailability of manpower, and thus automated solutions might be more suitable for such project sites.
Apart from manual methods such as spraying water with hosepipes, tractors or buckets, various mechanical, coating and electrostatic techniques are currently used for cleaning solar Photovoltaic panels. Mechanical techniques can be further categorised into air-blowing, robotic, water-blowing and ultrasonic vibration methods. All of these methods involve moving parts and require power for their operation.
Coating and electrostatic techniques are more advanced compared to mechanical methods of cleaning, and significant research is underway to develop cost-efficient cleaning technologies in these two areas. Coating involves applying a thin film of hydrophilic and hydrophobic nanoparticles on the solar panel surface. While hydrophobic coating makes water roll off the surface of the panel, carrying dust and other impurities along with it, hydrophilic coating reduces the deposition of dirt through a photo catalytic reaction. Titanium oxide is a material often used for such coatings.
Coating is highly beneficial as it reduces the water and labour requirement for cleaning. Its main advantage lies in its ability to keep the panel surface clean for extended periods, thereby enhancing project performance. Moreover, when this technique is combined with mechanical methods, the results are even more effective. However, coating as a cleaning method is still in the early stages of development, and it will take some time for this to gain mass popularity.
Reportedly, Jakson Green has applied nanocoating at a few of its projects, and according to Navdeep Singh, head of O&M at the company, significant gains were achieved in the performance of the coated solar modules compared to the uncoated ones. In fact, a generation gain of 3-4 per cent was observed over the course of six months at the same location and during the same cleaning period. According to him, the drawback is that the coating is quite expensive, and the payback period is approximately five to six years. Going forward, the reliability and effectiveness of these coatings are expected to increase, and it is anticipated to become more cost-competitive for greater adoption.
Further, certain electrostatic techniques are also being utilised for cleaning solar panels. These include the electrodynamic screen cleaning technique, which uses electric curtain boards to expel dust from the solar panel’s surface. Another technique involves an electrostatic induction charge on dust particles that causes their repulsion. Like coating, these technologies require further research and development for them to gain greater traction.
There is significant innovation under way to develop efficient and cost-effective techniques for cleaning solar modules. For instance, the paper, “Experimental Investigation of a New Solar Panel Cleaning System Using Ionic Wind Produced by Corona Discharge”, published in the Journal of Electrostatics in July 2023, discusses the performance of 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. In this system, dust 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 surface. Researchers at the University of Jordan 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.
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 will be on reducing water usage and manpower deployment.
Robotic module cleaning solutions have gained significant popularity across the globe, even in price-sensitive markets like India. Additionally, waterless products are now available at competitive prices. As expected, the adoption rate is higher for large utility-scale projects, where the project scale is much larger than smaller rooftop projects, making it more commercially viable to deploy advanced technologies.
A key factor to consider is the availability of skilled technicians and engineers capable of effectively utilising these advanced technologies. While automation will reduce manpower requirements, skilled labour will still be required to manage these advanced tools and ensure their effective operation. Moreover, this necessitates the upskilling of manpower to address any issues that may arise while using these technologies.
It is expected that like robotic technologies, coatings and electrostatic techniques will also gain popularity in the years to come. 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 to ensure the optimal performance of solar panels.
