The Cleaning of Solar Modules as Part of the Energy Production: Justifications and Techniques

For many years, the common believe was that the natural inclination of solar panels with the help of some precipitations would result in an automatic cleaning. Measurements however show that the energy output of solar modules reduce drastically when they are dirty. On an 800kW plant, the accumulated dirt on the panel within a year led to a decrease of 30% of the productivity. To prevent this, several techniques are being used, each having pros and cons. Among them, hand washing was the most common technique for cleaning panels. However, with the multiplication of large-scale installations, this business model is being questioned. Lack of efficiency, rising cost of labor, risky working conditions, panels even getting dirty again before the work is completed… Hand washing the panels can no longer be considered to be the only answer to persistent soiling. A second type of cleaning solution is the use of large scale brushes mounted on vehicles. These brushes allow cleaning of panels set up in lines with enough distance between them to let the vehicle pass through. Also, it can only clean panels up to a certain height, limited by the length of the articulated arm manipulating the brush. Despite this, it remains one of the quickest ways to clean large scale utilities. A third type of cleaning solution uses on-panel gliding machines that pass from one side to the next of the line. These machines can be automatized to run at specific times of the day or night. However, they cover only one line, which induces a large investment or the use of man power to transfer the tool from one line to the next. Also, this is only applicable to specific installation mounting types. Lastly, cleaning can also be performed with robotic solutions. These can be fully automatized or semi-automized and controlled by a user. In any case, they allow for faster cleaning with less physical strain. Also, it is the most versatile solution, as robots can be set up on all installations (ground-mount, roof-top, carport, floating panels, etc.) without set up restrictions. It is also an evolving solution that can be adapted and customized for each type solar module configuration.