AC/DC Electroluminescence. The War of the Currents

Solar photovoltaic energy has emerged as a pivotal solution to address global energy challenges, offering clean and sustainable power sources. However, ensuring the quality and reliability of photovoltaic modules is paramount to optimize the efficiency and longevity of solar systems. This necessitates precise characterization of modules and photovoltaic plants, with early detection of faults becoming crucial for maintenance and productivity. Among defects, cell-level anomalies can lead to significant failures and long-term repercussions on surrounding PV modules. Conventional defect detection methods, such as high-resolution electroluminescence (EL) imaging using direct current (DC) polarization at short-circuit current (Isc), face limitations in detecting latent anomalies like poor soldering joints or potential induced degradation (PID). To address these limitations, an innovative approach employing alternate current (AC) polarization signals for EL imaging is proposed. This method enhances defect visibility and enables comprehensive defect analysis, including hotspots, cracks, degradation zones, and PID occurrences. The approach allows simultaneous polarization at the effective short-circuit current (Isc_RMS) and its 10% equivalent, facilitating thorough defect analysis. Preliminary results, conducted at the Enertis Applus+ laboratory, demonstrate the identification of previously undetectable disconnected areas not detectable through conventional methods. Moving forward, the goal of this work will be to conduct a more in-depth analysis of other widespread defects such as PID and poor soldering.