Robots That Clean Solar Panels Without Water

There is a problem with solar farms: the panels must be cleaned often to retain efficiency, but that raises the problem of water waste. It’s a big conundrum, especially in arid areas where many solar farms are located: You have less water and more dust to clean from the panels.

Allouche founded Airtouch Solar in 2017 to address increasing worldwide demand for a dry-cleaning robot for solar panels, their autonomous, water-free, robotic cleaning systems are boosting solar energy output by up to 30 percent for clients in Israel and India thus far.

The secret sauce of Airtouch Solar’s robots is a patented air blower that lifts and pushes the dust forward horizontally along arrays of panels. The dust falls into the gaps between each cluster. Following close behind are soft towels that remove any remaining particles.

“When you clean left to right, you enjoy a lot of benefits. It’s faster and consumes less energy, among others. But you’re carrying a lot of dust along the way,” says Allouche.

“Most of the heavy dust is removed by the blower in the direction of the cleaning, so the towels only need to finish the job.This allows us to use very gentle microfiber instead of brushes. The fabric not only cleans better, but also minimizes micro-scratches.”

Micro-scratches — caused by dragging scratchy sand particles across the surface in the frequent cleaning process — deteriorate the antireflective coating on the panels, making them less able to absorb solar rays.

And how is the microfiber itself cleaned? Allouche says a mechanism shakes the fabric out during each cleaning cycle, a process aided by the action of the air blower.

Each deployed robot is connected to the company’s IoT (Internet of Things) system so the process can be programmed and controlled remotely for the client, allowing for real-time adjustments based on forecasted weather, wind speed and rainfall. It’s done without unnecessarily complicated technology such as sensors.

A major green advantage of the Airtouch Solar robotic cleaner: the system is self-sustaining, powered by the very solar panels it cleans.

“The robots have rechargeable batteries that are charged during their ‘sleeping mode’ from the solar panels,” says Allouche, explaining that typically the robots work for an hour each day and “sleep” the other 23.

Furthermore, the blowing effect is achieved by a geometric mechanism “that doesn’t require a lot of power or down time and functions well in a desert climate.”

Airtouch Solar’s design is unique, but it does have competitors in China and in Israel – most notably Tel Aviv-based Ecoppia, a nine-year-old industry pioneer that recently won an Environment + Energy Leader Award for its H4 waterless PV panel cleaning robot.

Solar energy is a hot technology these days, while water is a dwindling resource.“Israel and many countries are currently recalculating their course in order to adopt clean energy sources, such as those derived from the sun, as part of a growing transition towards these sources. Our solutions help alleviate the fear that the drought and water crisis will delay the transition to renewable energy sources,” says Laufer.

South African researchers have developed a new cleaning system for solar panels that uses a color-sensing light-to-frequency converter to detect dirt. It can reportedly remove around 95% of the dust from a PV panel in less than a minute, at a lower cost than other systems.

Researchers from the University of Johannesburg in South Africa have developed a cleaning system for solar modules based on the TCS3200 color sensor and the Arduino Uno open-source microcontroller.

The TCS3200 is a programmable color light-to-frequency converter equipped with white light-emitting diodes (LEDs) to illuminate an object's surface for color detection, with the object reflecting light to the sensor to determine color intensities.

“TCS3200 can detect the color of the light incident and output square waves with 50% duty cycles,” the scientists said. “Compared to other scientific instruments, this sensor is reasonably at a low cost.”

The microcontroller is the key element of the entire system, which also includes a 46 V motor driver, two 12 V DC motors, a charge controller, a rechargeable battery, a voltage regulator, and a roller brush.

“The roller brush provides a sweeping motion for cleaning the panel surfaces by spinning at a higher speed than the movement wheels,” said the research team.

The system also uses Arduino IDE software to write, compile and upload sketch codes for the system. It includes the connecting rods, the case shielding the electronic components, and the brush-driving devices.

The system can detect dirt on solar panels by measuring colors, calibrating colors, and comparing measured results with reference results.

“When the controller detects that the humidity threshold level signal has reached 80%, the motor driver will turn on to clean the solar panel,” the academics explained. “Motor A of the two DC motors in the setup moves the color sensor across the solar panel for color monitoring, while Motor B drives the cleaning robot to remove dirt.”

The group estimates annual system costs at €1.50 ($1.60) per panel, with capital and maintenance costs accounting for most of the associated costs.

“In one minute, up to 95% of the dust on the PV panel surfaces can be removed by this device,” claimed the group.

The scientists described the new cleaning system in “Solar panel surface dirt detection and removal based on Arduino color recognition,” which was recently published in MethodsX.

“The researched project is an improvement over existing systems since it eliminates many of the drawbacks, such as the need for water, manual cleaning, the need for labor,” the scientists concluded. “The system can operate for many years before requiring maintenance.”

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