A modeling framework for potential induced degradation in PV modules

Abstract

Major sources of performance degradation and failure in glass-encapsulated PV modules include moisture-induced gridline corrosion, potential-induced degradation (PID) of the cell, and stress-induced busbar delamination. Recent studies have shown that PV modules operating in damp heat at -600 V are vulnerable to large amounts of degradation, potentially up to 90% of the original power output within 200 hours. To improve module reliability and restore power production in the presence of PID and other failure mechanisms, a fundamental rethinking of accelerated testing is needed. This in turn will require an improved understanding of technology choices made early in development that impact failures later.In this work, we present an integrated approach of modeling, characterization, and validation to address these problems. A hierarchical modeling framework will allows us to clarify the mechanisms of corrosion, PID, and delamination. We will employ a physics-based compact model of the cell, topology of the electrode interconnection, geometry of the packaging stack, and environmental operating conditions to predict the current, voltage, temperature, and stress distributions in PV modules correlated with the acceleration of specific degradation modes. A self-consistent solution will capture the essential complexity of the technology-specific acceleration of PID and other degradation mechanisms as a function of illumination, ambient temperature, and relative humidity. Initial results from our model include specific lifetime predictions suitable for direct comparison with indoor and outdoor experiments, which are qualitatively validated by prior work. This approach could play a significant role in developing novel accelerated lifetime tests.

Radiative sky cooling: fundamental physics, materials, structures, and applications

“…For the short term, the elevated temperature directly reduces the power conversion efficiency of PV cells, for example, temperature coefficient of −0.45%/°C for crystalline silicon. In the long run, the aging rate for solar modules can double with every 10°C increase in average temperature [77], caused by thermally activated degradation processes, such as corrosion and potential-induced degradation [78,79]. Hence, cooling photovoltaic cells can dramatically improve performance and reliability, leading to greater energy yield.…”

Real‐time monitoring and diagnosis of photovoltaic system degradation only using maximum power point—the Suns‐Vmp method

“…Recently, several physics-based degradation models have been developed that can directly map various PV degradation modes (eg, corrosion, PID, yellowing) to the temporal behavior of circuit parameters. 48,49 The extracted circuit parameters by the Suns-Vmp method can be used to calibrate these degradation models (eg, moisture diffusion coefficient for corrosion). Integrated with the weather forecast, the calibrated degradation models will predict the lifespan of solar modules.…”

“…In this regard, the Suns-Vmp method can facilitate accurate reliability prediction. Recently, several physics-based degradation models have been developed that can directly map various PV degradation modes (e.g., corrosion, PID, yellowing) to the temporal behavior of circuit parameters [47], [48]. The extracted circuit parameters by the Suns-Vmp method can be used to calibrate these degradation models (e.g., moisture diffusion coefficient for corrosion).…”