Advanced imaging pinpoints solar panel defects

Current methods for defect detection in silicon solar panels, which currently account for 90% of all solar panels produced, require nighttime or shaded conditions. An inspection approach that can be deployed under bright sunlight and accelerate the identification of imperfections has been developed by researchers from Nanjing University of Science and Technology in China.

The all-weather imaging system, applicable under any lighting conditions, renders defects visible by use of software that delivers a modulated electric current to a solar panel, causing it to emit light that turns off and on very quickly. An indium gallium arsenide detector with a very high frame rate acquires a sequence of images of the solar panels as the electric current is applied. The system includes a filter that limits the wavelengths detected to those around 1150 nm 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," explained the researchers. "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."

When applied to both monocrystalline silicon and polycrystalline silicon solar panels, the system described in Applied Optics was demonstrated to detect defects on silicon-based solar panels with irradiances from 0 to 1300 W/m2, equivalent to light conditions ranging from complete darkness to full sunlight.