Renewable energy has become a major aspect of development agendas of countries around the world. As per the International Energy Agency, the use of renewable energy increased by 3 per cent in 2020, corresponding with a decline in demand for all other fuels. In 2021, renewable power generation is expected to experience the fastest year-on-year growth since the 1970s, with over two-thirds of the contribution coming from wind and solar photovoltaic (PV) alone. Solar PV has emerged as one of the fastest growing sources of electricity in recent times. National targets, supplemented by the onset of international collaborations such as the International Solar Alliance, have fostered the growth of solar power. In India, for instance, a major push to renewable power has come from solar energy, given the country’s target of installing roughly 300 GW of solar power by 2030.
Operation and maintenance (O&M) activities are integral to the long-term sustainability and efficiency of solar plants. External influencers such as dust, dirt, pollen, high temperatures, shadows and bird droppings often hamper the generation of power via solar PV panels. For solar power to be effectively utilised, these environmental factors must be kept in check. As dust can interfere with the level of sunlight absorbed by a solar panel, accumulation of dust is one of the biggest threats to effective power generation from PV panels. A 2013 paper by Travis Sarver, Ali Al-Qaraghuli and Lawrence L. Kazmerski highlighted how poor air quality can significantly deteriorate the energy yield of PV panels. In the absence of cleaning, dust and pollution can cause a decrement of up to 6.5 per cent in energy production by the panel. A 2017 study by Hussain et al. states that due to greater accumulation of dust in arid regions, the reduction in solar efficiency can be approximately 40 per cent. The removal and cleaning of dust and soil from solar panels also contribute considerably to the total O&M costs associated with solar plants. Cleaning solutions, thus, becoming an essential tool to ensure efficiency in solar generation.
The water vs solar debate
While electricity generated through solar power plants is free of greenhouse gas emissions, it entails certain detrimental impacts on the environment, especially in terms of overutilisation of local water and land degradation. The use of water in the cleaning and maintenance of solar panels has raised concerns regarding the true “green” nature of solar technology.
According to a 2019 study by Bridge to India, over 56 per cent of India’s solar capacity has been installed in areas that are arid and comprise several high-water-stress zones. While the amount of water needed for cleaning a solar panel is typically 3-5 litres, it increases to 7-8 litres in arid regions. The study also found that over 60 per cent of the water used in solar installations is derived from bore wells and underground sources of water. Many of the states where solar plants have been established, such as Rajasthan, Karnataka and Gujarat, already consume high amounts of water. With India on the path of rapid development and growth, the demand for water will continue to rise. Despite large sources of fresh water in the country, it continues to be water scarce. Many Indian cities are anticipated to run out of groundwater in the near future. By 2030, the demand for water in India is projected to be double the supply. The increasing demand can also be seen in the sharp rise in the price of water over the past few years. This has induced certain developers to rely on illegal means to access water, leading to exploitation.
The problem of water scarcity is expected to be exacerbated with a rise in dust storms and frequent variations in climatic conditions. Dust storms may significantly increase the need for water for solar panel cleaning, if alternative technologies are not adopted. Therefore, the Ministry of New and Renewable Energy has pushed states to adopt solar cleaning technologies that can enable optimal utilisation of water. In an effort to reduce overconsumption of water in the solar sector, the industry is also witnessing a shift towards robotic cleaning solutions that use minimal or no water for maintenance of solar panels. Several solar developers are now adopting robotic technology for cleaning. In April 2021, Israel-based clean solutions providers for solar systems Airtouch Solar signed an agreement to supply water-free robotic cleaning systems to be applied at three new solar PV plants of ReNew Power in Rajasthan.
All stakeholders, including the government, solar developers and operators, must push for policies and technologies that minimise the consumption of water. Eliminating over consumption of water in solar panel cleaning is necessary to ensure that the use of one green technology does not negate the conservation of another integral resource. Only then can solar power be truly considered as green power.
Technology overview and progress
As per the Global Market Insights Report 2020, the solar panel cleaning market is expected to achieve a compound annual growth rate of over 11 per cent through 2026.
The process of cleaning ensures that the power conversion capability of solar PV is not hampered due to accumulated dust or other environmental obstructions. This, in turn, enhances and maintains productivity and efficiency in output. Cleaning technologies can be broadly classified in terms of operation as manual and automatic. In terms of process, they can be primarily categorised as water based, electrostatic and robotic. The traditional water-based cleaning solutions entail manual input and heavy usage of water, often leading to inefficiencies in the utilisation of water resources and higher O&M costs. Electrostatic solutions use electrostatic charge material over the solar panels, along with sensors that monitor the level of dust. More recently, robotic cleaning and anti-soiling coating have been developed and adopted rapidly to maximise energy output and reduce the dependence on water and labour. These technologies are now technically and commercially proven.
As per a 2020 paper by Kazem et al. to ensure the economic and technical feasibility of solar projects, it is crucial to make the choice of cleaning solutions based on plant size, location, environmental and seasonal factors as well as the dust density in the region. Traditional cleaning, for instance, has been found to be feasible in small-scale plants, but is otherwise costly and inefficient. The climate of a region also determines the type of dust accumulated on solar panels and its impact on generation. In tropical regions, dust particles may transform into dew in the morning due to greater moisture in the atmosphere, and naturally clean the panels. However, in certain regions, dust particles may be sticky and difficult to remove. In the former case, waterless methods can be used, while in the latter, water-based methods may be more effective.
While the traditional segment of solar panel cleaning is expected to grow due to its feasibility and wide applicability across different conditions, the industry is witnessing a shift towards automated and waterless cleaning solutions. Stringent government regulations are being put in place to prevent precious water resources from being depleted. Greater environmental consciousness among consumers and producers is also paving the way for faster adoption of waterless and green cleaning technologies to remove dust and dirt from solar panels. Waterless and robotic methods include mechanical brushes, standing wave electric curtain systems, heliotex technology, nano-film, cloud computing and internet of things. These solutions are capable of reducing water consumption substantially, contingent on the type of method adopted. Consequently, the industrial landscape is swiftly transitioning towards advancements in waterless cleaning solutions.
Lessons from Covid-19
Despite the continuous growth witnessed in the sector, the emergence of the Covid-19 pandemic has posed several new challenges for the renewable industry. These include lack of mobility and communication, barriers in production lines and limited supply of manned labour. Restrictions due to lockdowns and government regulations have highlighted the need to shift to automation. As per the estimates of the Council on Energy, Environment and Water, solar plants in India need to be cleaned at least once a week, especially in dry and arid regions. Dependency on human labour in such cases may lead to inefficiencies in solar power output if panels are not cleaned in a timely and effective manner due to restrictions on labour supply.
The pandemic has opened up new avenues for robotic technologies and artificial intelligence to be adopted in various sectors, including the solar industry. There is now a rising demand for quick and effective cleaning technologies that require minimal supervision and no manual input. Automated and unmanned cleaning machines are also expected to minimise human errors in solar power O&M. These automated technologies may provide high performance outcomes and greater reliability under extreme weather conditions, along with faster cleaning and lower operational costs. Therefore, in the coming years, the solar industry can expect an increase in demand for robotic cleaning solutions.
The rapid adoption of solar energy along with the rising demand for advanced solar technologies will pave the way for greater investment in the solar sector in the near future. Solar energy can play a pivotal role in India’s renewable transition, given reforms and regulations that ensure optimal utilisation of resources, keeping the “green” characteristic of solar energy intact. The government can play a significant role in encouraging the adoption of efficient cleaning technologies and promote R&D in the local production of robotic and automated solutions. Fiscal benefits may also be offered to supplement positive consumer demand. As greater emphasis on the reduction of carbon emissions could translate into the deployment of large-scale solar projects, a focus on cost minimising technologies and cleaning solutions is essential. Ultimately, efforts must not only be oriented towards installation but also towards various segments of O&M to maximise output in the overall solar segment.