Although solar panels are believed to not require much maintenance, this is true only in areas that receive adequate rainfall. The majority of solar projects in India are located in remote, arid regions with high levels of ambient dust. Dust accumulation on panel surfaces has a shading effect which, in turn, affects performance. A 2017 field study by M.H. Bergin et al, in collaboration with the Indian Institute of Technology Gandhinagar, found that atmospheric particulate matter deposited on the panels resulted in a 17-25 per cent drop in power generation. The prevalence of large amounts of dust makes panel cleaning a regular feature of plants’ operations and maintenance (O&M) in order to maintain optimal efficiency.
However, the lack of adequate water in these dry, arid regions poses a big challenge both in terms of availability of funds as well as manpower required for cleaning panels. Although water consumption levels in solar plants – roughly 100 litres for 1,000 units of electricity – are 22 times lower than in thermal power plants, water procurement is a considerable operational burden for solar units. For plants that use surface water, the annual cleaning cost can be as high as Rs 100,000 for every MW of installed capacity. According to a study by Bridge to India, a renewable energy research firm, about 60 per cent of the water used for solar panels is procured through borewells. The use of borewell water, however, has its own set of challenges and cost implications. While cleaning with hard water damages the panels by scaling at the corners and leads to the formation of black spots, cleaning with detergent and wipes destroys the anti-reflective coating, which in a way deflects the sunrays and reduces power generation.
With solar project developers having compromised on their margins by quoting low tariffs to bag projects, the rising costs of water further threaten to hurt project profitability. Some solar developers in Rajasthan have seen water costs almost doubling in the past three to four years. In Karnataka, tariff for industrial water usage was hiked 100 times in 2018. Hence, cleaning costs can be significant, comprising 25-35 per cent of O&M costs of a plant.
A rapidly emerging solution to these challenges is water-free robotic panel cleaning, which offers major potential savings in vehicle, water and labour costs. Water-free autonomous technology can also help reduce soiling losses by cleaning faster and producing higher quality results than manual cleaning methods. Traditional manual cleaning is done once in 15 days and is thus not the most effective solution. In contrast, robotic solutions can clean solar panels every day, or on demand, without any substantial human intervention.
The application of robotic cleaning solutions becomes more cost economical with the increase in project size. The larger the project, the greater will be the cost of manual labour for panel cleaning. Realising this, most utility-scale project developers and solar park operators have started opting for automated solutions. Take, for instance, the case of the Kamuthi solar facility in Tamil Nadu, which has a total power generation capacity of 648 MW. Covering 2,500 acres and consisting of 2.5 million solar panels, the site is estimated to produce enough power for 750,000 people. The plant is cleaned every day by a robotic system, which gets charged by itself through inbuilt solar panels.
A number of companies, both domestic and international, are offering these solutions in India. Tel Aviv-based Ecoppia has been one of the early entrants in the Indian dry robotic cleaning space. NTPC’s 5 MW plant in Dadri had Ecoppia build a fully automated water-free solar panel cleaning system. Ecoppia’s device is attached to the panel where it moves over the surface, clearing the dust with microfibres.
In fact, Ecoppia has been providing its water-free cleaning robotic solutions to a number of utility-scale solar project developers in the country. In mid-2018, Ecoppia signed an agreement with SB Energy to install around 2,000 robots across its five project sites at the Bhadla Solar Park (Phases III and IV) in Rajasthan. The Bhadla project is in a water-deficient region and often faces massive dust storms. This increases the panel soiling resulting in reduced energy output. These robots work independent of human interference and can be remotely operated through a cloud-based control system. It is estimated that Ecoppia’s water-free technology can save over 2 billion litres of water over the solar plant’s 25-year operational life.
US-based SunPower is another company which offers its minimal-water usage based robotic cleaning systems in India.
Among domestic players, there are companies offering water-less as well as water-based solar panel cleaning solutions. Kapson Tekno Engineers offers solar cleaning rollers made of scratch-resistant microfibre stretchable cloth. Their solar cleaning rollers, iXC-12 robot, travel on a track specially created on the mounting frame. Once these tracks are installed, they take care of uneven landscaping, uneven panel installations and gaps between the panels.
Domestic companies, although small, are gaining traction on account of the growing demand for these solutions and attracting investments. The latest is Noida-based start-up Skilancer Solar, which has raised an undisclosed amount from angel investor and serial entrepreneur Dhianu Das’s venture capital fund Alfa Ventures. Skilancer Solar offers autonomous robots powered by artificial intelligence (AI) for cleaning solar panels.
A number of semi-automated cleaning methods are gradually replacing manual ones with improved efficiency and costs. For instance, Mumbai-based Inspire Clean Energy has designed a cleaning brush, which effectively cleans a module with minimal water consumption. In fact, it uses only about 300 ml of water to clean a module as against 5-7 litres used in manual cleaning.
Summing up, considering the cheap labour costs in India, robotic cleaning might not gain traction in the near future; however, these solutions will increasingly become common. At present, these are being used for large utility-scale plants with large amounts of dust, water scarcity and cost issues. As the cost of these solutions decreases with the increase in their scale, they will become cost effective for smaller-scale plants including rooftop installations.
By Dolly Khattar