Low-Current Diagnostic Metric for Photovoltaic Module Damage

Ryan M. Smith1& Dylan Colvin2,3 1Pordis LLC, Austin, TX, United States /2University of Central Florida, Orlando, FL, United States /3Florida Solar Energy Center, Cocoa, FL, United States

High-throughput, inexpensive, and reliable diagnostic techniques are necessary across all stages of photovoltaic device manufacture and lifetime. Dark current-voltage (I-V) sweeps are relatively simple to perform and provide a wealth of information on device characteristics. Complete dark I-V curves may not be necessary for successful monitoring of specific damage and degradation modes, such as low-current shunt effects due to cell fracture. We propose a new diagnostic technique which identifies module damage in the low current regime by monitoring changes in the voltage required to achieve a single specific current injection. Preliminary results demonstrate that this metric, called 'V10', decreases significantly with module damage. In the first experiment's most damaged condition, V10 decreased by 32.5% while the light I-V maximum power only decreased by 5.4%, thereby demonstrating the high sensitivity of low-current performance and therefore the proposed technique. A subsequent real-time V10 monitoring experiment showed an immediate decrease in V10 (1.35%) corresponding to the module's impact with the ground after purposely allowing the module to fall under its own weight. Requiring minimal power, V10 presents an  efficient diagnostic tool for detecting damage in PV modules during mechanical damage events with promising applicability to in-situ monitoring during accelerated stress testing, transportation, installation, field performance monitoring, and re-powering activities.