Keeping Modules Clean

Solar O&M market, costs and key issues

Unlike project development and execution, which take one to two years, a solar project’s operations and maintenance (O&M) phase continues for the entire 25-year life of the plant. Efficient O&M, thus, is critical for mitigating risks, and ensuring project quality and the required returns on investment. For this reason, solar O&M has become a key focus area for the solar industry in recent years, emerging as a separate market with its own ecosystem, trends and dynamics. A large number of third-party solar O&M service providers have entered this space, offering customised service packages to developers at attractive prices. Meanwhile, growing economies of scale and increased integration of automation and digitalisation have been driving down O&M costs over the past few years, a trend that is likely to continue.

Along with the decline in solar O&M costs, a change has been witnessed in the cost composition itself, on account of the increasing use of automation and the consequent decrease in dependence on manpower. This trend has been accelerated by the Covid-19 pandemic, which has highlighted the importance of having efficient remote monitoring services and automated maintenance equipment that does away with or reduces labour requirements. Thus, although manpower still constitutes the bulk of the total O&M cost, its share is gradually declining. Even module cleaning, which comprises a significant portion of the O&M work and is one of the most critical and time-consuming services, is now being increasingly automatised.

In the Indian scenario, where most large projects are located in the dry and sandy regions of Rajasthan, Gujarat and Madhya Pradesh, dust deposition is a major cause of performance loss in solar panels, necessitating regular cleaning. Even in other parts of the country, high levels of pollutants and dust coat the solar panels, impacting performance. When rain or dew combine with this fine dust, it becomes even harder to clean the panels. In the mountains, too, snow or ice can accumulate on the solar panels, impacting performance. In fact, according to studies, dirty solar panels can reduce solar plant efficiency by more than 30 per cent and in arid regions, losses due to soiling can reach up to 25 per cent through just seasonal rain and dust. Hence, module cleaning is an important O&M activity, contributing to nearly 30 per cent of total O&M costs depending on the quantity of water utilised, equipment used and manpower employed.

Module cleaning techniques

The frequency of module cleaning and the technique used often depend on the project site. For instance, modules at sites located close to mines have to be cleaned at least once a week, while those in regions that receive regular rainfall can be cleaned just once or twice a month. Although water consumption levels in solar plants are over 20 times lower than in thermal power plants, the volumes are still phenomenal, adding to operating costs. In many arid and semi-arid regions especially, water is a very costly resource because of which plant operators are forced to reduce the frequency of module cleaning. This affects project returns substantially. Thus, there is a need to have water lines in place prior to the commissioning of a plant. In projects where surface water is unavailable, groundwater from borewells is often used for module cleaning.

Historically, most solar projects in India use tractors or hosepipes to spray water on the panels. However, these conventional cleaning methods are both water- and labour-intensive, while also being time-consuming. Thus, there has been a rise in module cleaning solutions that optimise water use, decrease labour requirements, or both, so as to save on operating costs. Various robotic solutions and cleaning technologies have thus emerged that can minimise manpower dependence, avoid water wastage and improve efficiencies. Many of these technologies use artificial intelligence and are automated to the extent that they can self-assess the cleaning requirement by analysing dust deposition patterns and electricity generation data, subsequently carrying out O&M activities on their own.

Israel-based Ecoppia, for instance, offers various robotic module cleaning solutions that are completely automated and can be monitored remotely. One of its products is a microfibre-based cleaning device that can be attached to a solar panel and cleans it by moving over its surface. Similarly, ArcelorMittal-owned Exosun supplies battery-operated robotic cleaning solutions for solar panels that perform best when operated in pairs. While one robot is cleaning a panel, the second gets attached to a new panel. Inspire Clean Energy, another Indian solar O&M company, has developed a cleaning brush that can effectively clean a module using very little water. Yet another domestic company, Skilancer Solar, has built a self-powered automatic robot that requires no manual intervention to operate.

According to industry estimates, the costs vary significantly for each of these different techniques. They are the highest when tractors are used to spray water, and while free access to water reduces these costs significantly, the manpower requirement keeps them high. Meanwhile, using a wet brush on a vehicle to clean modules greatly reduces both labour and water costs. These can be further reduced with the help of robotic technologies. Although fully automatic robots are costly at the moment, even semi-automatic ones can significantly lower manpower and water requirements. These robotic technologies are likely to become more economically viable in the near future as advancements and scale bring costs down, further encouraging their uptake.

Key challenges and outlook

Despite the diverse variety of techniques, a number of challenges make it difficult for operators to carry out efficient module cleaning. One of the most critical issues is unavailability of water at project sites, especially in the remote, arid regions of the country. With projects exceeding hundreds of megawatts in size coming up in the desert regions of Rajasthan, Gujarat and Ladakh, the situation is going to exacerbate in the future, especially with the overusage of groundwater and sinking of water tables in certain areas. In many cases, the available water also needs to be demineralised to make it fit for module cleaning, which further increases operating costs. For this reason, techniques that use little or no water are being researched and even commercialised, albeit to a small extent. Further, the skilled manpower required for carrying out O&M services is expensive, especially in remote regions, thus strengthening the use case for robotic technologies.

However, the drawback with both waterless and automatic solutions is that they are too expensive to be viable, particularly for small-scale rooftop solar plants. While many large-scale projects use automated solutions for module cleaning, the costs need to be reduced further for wide-scale adoption. Going forward, it is expected that the Covid-19 experience and issues surrounding manpower and water unavailability will lead to a shift in the industry-wide perception of these advanced technologies, increasing their uptake.

By Khushboo Goyal

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