High Throughput Outdoor Photoluminescence Imaging via PV String Modulation

Outdoor Photoluminescence imaging of crystalline silicon photovoltaic modules in full daylight via contactless switching of the operating point was recently demonstrated. That previous method requires an optical modulator to be placed on at least two positions of each module under test and two or more separate sets of image pairs need to be acquired and combined into a merged PL image.Here we demonstrate a modified approach which enables outdoor PL image acquisition of an entire module from just one image pair. The method still enables image acquisition without any modification of the electrical wiring within the system but is overall simpler and thereby enables significantly higher sample throughput for outdoor PL image acquisition in PV power plants. It also enables imaging of several PV modules at once. The method relies on partial shading of up to five series connected modules and PL image detection of the remaining non-shaded series connected modules within the same module string. In this paper the underlying principles and technical details of this novel method are discussed. Experimental data demonstrating the feasibility of the method are presented, including PL images acquired on state-of-the art bifacial half-cell PV modules.