New solar panels can be cleaned without water

A recent sand cloud in the Sahara that covered much of France in a thin layer of orange dust has raised questions about solar panel cleaning around the world. Many of thesunny fields” are located in desert areas and are already subject to this recurring problem, which is likely to get worse with climate change. At present, cleaning with water is effective, but not very durable and very expensive. An MIT study developed a system to overcome these problems.

Historical and global problem

This is on the agenda of many energy transition plans around the world: “Solar energy is expected to reach 10% of global electricity production by 2030” explains the study. Most large solar installations, such as those in China, India or the United States, are located in desert areas where solar radiation is at its highest, but dust is everywhere. Particle settling can result in up to 30% less crop loss within a month without cleaning. “For a 150 MW solar installation, even a 1% reduction in power could result in a loss of $200,000 in annual revenue.”, say the researchers. Therefore, panel cleaning is critical to the future efficiency and profitability of solar energy.

Excessive water intake

Typically, the panels are cleaned with clean, pressurized water, which is often delivered to the site. “It is now estimated that about 38 billion liters of drinking water per year is used to clean solar panels, enough to supply two million people.MIT researchers explain. This poses several problems, especially in terms of drinking water shortages in regions already suffering from drought. In terms of costs, an MIT study estimates that “cleaning with water is 10% of the operating costs of solar installations“. Before that, water was the best solution to clean the surface of the panels without scratches that could damage them and reduce efficiency.

Eget rid of water addiction

An MIT innovation that allows dry cleaning without the risk of scratches. This feat was made possible by the use of an electrode embedded in a metal rod. Passing a few centimeters from the panel, the electrode creates an electric field that charges the dust particles. The particles are then attracted to the rod when an electric field opposite to it is applied to the thin transparent conductive layer covering the panel. The applied tension is then precisely calculated to overcome cohesive and gravity forces and cause the dust to rise.

On the other hand, the effect requires a minimum of humidity. A thin layer of water covering the dust particles acts as a conductor, and then the system is really effective only at 30% humidity, at which the particles are not attracted. “Even in the driest deserts, the humidity is usually higher early in the morning, leading to dew formation, so cleaning can be timed accordingly.” explains one of the researchers. The idea is to equip each solar panel with a motor, using a tiny fraction of the electrical production of the panel itself, thus eliminating any cleaning intervention.

Diagram of a device that allows for waterless cleaning of solar panels, developed by the Massachusetts Institute of Technology. (source: Science and Future)

Video illustrating the attraction of dust particles to a metal rod (Source: Facebook MIT Mechanical Engineering)

“By eliminating reliance on water delivery from trucks, eliminating dust buildup and reducing overall operating costs, such systems can significantly improve the overall efficiency and reliability of solar installations. If the solar industry takes the initiative and approaches this problem in a comprehensive manner, this will not have a direct impact on the population’s access to drinking water.”the researchers conclude.

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