Researchers have developed and demonstrated a new system that can detect defects in silicon solar panels in full and partial sunlight under any weather conditions. Because current defect detection methods cannot be used in daylight condi­tions, the new system could make it much easier to keep solar panels working opti­mally. Silicon solar panels, which make up around 90 percent of the world’s solar panels, often have defects that occur during their manu­facturing, handling or instal­lation. These defects can greatly lower the effi­ciency of the solar panels, so it is important that they be detected quickly and easily.

The researchers from Nanjing University of Science and Techno­logy in China created a unique combination of new hardware and software that allows defects in solar panels to be clearly imaged and analyzed even in bright light. “Today’s defect detection systems can only be used to find defects at night or on solar panel modules that have been removed and moved inside or into a shaded environment,” said Yunsheng Qian, who led the research team. “We hope that this system can be used to help inspectors at photo­voltaic power stations locate defects and identify them more quickly, so that these systems can produce elec­tricity at their maximum levels.”

In the new work, the researchers created an all-weather imaging system that works in any lighting condi­tions. To make defects visible, they developed software that applies a modulated electric current to a solar panel, which causes it to emit light that turns off and on very quickly. An InGaAs detector with a very high frame rate is used to acquire a sequence of images of the solar panels as the electric current is applied. The researchers also added a filter that limits the wave­lengths detected to those around 1150 nano­meters to remove some of the stray sunlight from the images.

“The very fast imaging speed allows more images to be collected so that a greater number of changes between images can be dis­tinguished,” said Sheng Wu. “The key development was a new algorithm that dis­tinguishes the modulated and unmodu­lated parts of the image sequence and then magni­fies this difference. This allows the defects in the solar panel to be clearly imaged under high irra­diance.”

To test the system, the researchers applied it to both mono­crystalline silicon and poly­crystalline silicon solar panels. The results showed that the system can detect defects on silicon-based solar panels with irradiances from 0 to 1300 Watts per meter squared, which equates to light condi­tions ranging from complete darkness to full sunlight. The researchers are now working on software to help reduce digital noise to further improve image quality, so that the detector can collect image changes more accurately. They also want to see if arti­ficial intelli­gence could be applied to the acquired images to auto­matically identify the types of defects and further streamline the inspection process. (Source: OSA)

Reference: S. Wu et al.: Defect detection system for silicon solar panels under all-day irradiation, Appl. Opt. 60, 8875 (2021); DOI: https://doi.org/10.1364/AO.435456

Link: School of Electronic and Optical Engineering, Nanjing University of Science and Technology, Nanjing, China