One of the most successful ways of moving towards renewable and non-polluting energy sources is by using solar panels to harness the sun’s energy for electricity generation. Solar panels are cost-effective with low maintenance requirements because they have no moving parts. Despite all their benefits, the efficiency of solar panels dwindles if dust, dirt and grime are allowed to accumulate.
According to a research paper titled “Design of Robotic Cleaning System for Industrial Solar Panel Arrays” (published November 2020) authored by Sachin Mathew, Maria Susan Abraham, Jishnu K.S. and Amina A., the biggest issue affecting the efficiency of a PV panel is dust, which can reduce its effectiveness by up to 30 per cent, depending on the environment. About 100 mg square metres of dust on a solar module can cause a 0.4-0.7 per cent production loss and a PV module can accumulate 80-300 mg square metres of dust each day. The annual energy losses caused by soiling range from 1.5 per cent to 6.2 per cent, depending on the location of the PV plant. Therefore, solar panels must be cleaned regularly if optimal power generation efficiency is to be maintained.
Module cleaning techniques
There are three types of solar cleaning technologies available to customers. The first method for eliminating dirt is to traditionally wash or wipe it away. A simple cloth can be used to clean the surface of PV panels for this purpose. This technique needs frequent and repeated procedures and can be extremely labour intensive.
The second method is semi-automatic cleaning, where solar power projects rely on both robots and manual labour. Semiautomatic systems are deployed for cleaning of solar panels, and robots are transferred manually from one row to another or from one table to another. These systems are best suited for solar panels installed on unlevelled ground, and tables that are not properly aligned and are not in continuity.
The third method is expected to dominate the market in the near future – a fully autonomous solution, with no manual intervention. Robotic cleaning gained popularity in India in 2019, when the Ministry of New and Renewable Energy released a letter advising the use of minimal water for cleaning utility-scale solar systems. The ministry suggested that solar projects should be cleaned using robotic cleaning equipment, which requires less water, whereas manually cleaning solar panels is dangerous and time-consuming.
Advantages of robotic cleaning systems
The Indian solar power market is expected to grow rapidly to meet its 2030 targets. It is considered that efficiency will be the most crucial factor in future projects, whether commercial and industrial, or utility scale.
These solar panel cleaning robots preserve solar power production efficiency by keeping solar panels clean without endangering human life. The robotic cleaning solutions are steadily gaining traction, and will get more economical as project sizes increase. Since the expense of manual labour for panel cleaning rises with the increase in project size, utility-scale developers and solar park operators are turning to automated cleaning solutions. Using robots also helps reduce water wastage.
Cleaning robots are often symmetrical, and their weight is evenly distributed, which helps them gain stability on the PV panel. Some existing autonomous robots in the global market are ineffective at cleaning PV panels due to their size.
Sand, construction dust, rocks, bird droppings and traffic emissions, as well as moisture, oil, fog and mist, make up the filthy layer on the PV panel surface. The thickness of the coating can vary depending on the installed set-ups. Thus, the ability to recognise soiling patterns and comprehend the level of soiling should be considered. It must be noted that as robots get more autonomous and precise, their initial cost increases. The power consumption of cleaning robots varies with the slope of the PV panel, wind speed, and thickness of the soiled layer.
Recent developments
Many companies are offering robotic solar panel cleaning solutions and this is fast becoming a highly competitive market. Some of these companies are Skilancer Solar, Heliotex LLC, Ecoppia, Sunbotics, Kambay Robotic, Solabot Robotics, Airtouch Solar, Parish Maintenance Supply, Kärcher UK Limited, BP Metalmeccanica, Solar Cleaning Machinery, Indisolar Products Private Limited, AX System, IPC Eagle, Integra Global Co., Limited, IDRIS Automation, Unger Germany GmbH and Aegeus Technologies. Solabot is an India-based manufacturing company that produces cleaning robots locally and supplies to more than 11 states for their different large-scale solar projects.
Airtouch Solar, an Israel-based public company trading on the Tel-Aviv Stock Exchange, develops cutting-edge autonomous, water-free robotic PV panel cleaning solutions for utility-scale solar PV installations. In April 2021, Airtouch Solar signed contracts to supply its water-free robotic cleaning systems for three of ReNew Power’s new solar PV plants in Rajasthan, to be commissioned by early 2022. The contracts entail the supply, erection, testing, commissioning, operation and maintenance of Airtouch robotic cleaning systems for 25 years and are valued at $7.6 million. The robotic cleaning systems for ReNew’s solar plants will be supplied from Airtouch’s production plant in Israel and the company’s manufacturing plant in India that is currently being established.
Ecoppia, an Israeli firm that specialises in robotic solar cleaning solutions, has its manufacturing base in India. In May 2021, Ecoppia announced in a first-of-its-kind trilateral venture that it would produce an innovative robotic solar cleaning technology in India for a landmark project in the UAE. In December 2020, Ecoppia announced signing a 450 MW project with Azure Power. The project is now at an advanced stage and was scheduled to go live at the beginning of the first quarter of 2021. Ecoppia secured new projects for more than 10 GW in the last four quarters despite the ongoing global pandemic.
Bengaluru-based Aegeus Technologies introduced the Shreem cleaning bot, which is specifically designed for rooftop solar installations. The robot is entirely self-contained and weighs only 5 kg (with batteries), making it small enough to fit in a backpack.
Outlook
As solar projects increase in size, cleaning of tens of thousands of solar panels regularly becomes a challenging task. In this case, cleaning manually with buckets, mops or hosepipes is not only impractical but also slow and inefficient. Thus, semiautomatic or fully automatic robotic solutions need to be considered in such cases for improving the cleaning efficiency and reducing the dependence on manpower.
The pandemic has taught us that relying completely on human labour for routine cleaning services is not ideal as a total shutdown of operations and maintenance works may occur in dire situations. In this case, having robotic solutions for cleaning can ensure that this critical maintenance work continues despite the unavailability of manpower.
Net, net, the robotic solar cleaning market is set to boom in the coming years as project sizes expand, complexity in maintenance increases and the industry adopts advanced automation to reduce costs.
