Degradation of individual cells in a module measured with differential IV analysis

Abstract

A methodology is developed for the extraction of cell-level properties from the analysis of differential IV response in a solar module with series connected cells. Through a combination of simulation and experimental verification we show that the shunt resistance and short circuit current of individual cells can be determined from a peak in the module differential resistance with cells that are partially shaded. The magnitude of the peak is equal to the shunt resistance of the cell for small values of shunt resistance. The current at which the peak occurs is proportional to the product of the short circuit current and the shading factor of the particular cell. With this methodology, we are able to measure degradation of 72 individual cells in a single commercial module after a high temperature/high humidity/high voltage stress test. Therefore, the statistics of degradation in this test were improved 72-fold.

A modeling framework for potential induced degradation in PV modules

“…This modular approach will allow researchers to quickly predict the performance of a new design or topology in a specific geographical location, even before the module has been assembled. Such an ambitious, transformative approach is necessary for predictive modeling of failure modes; otherwise, next-generation PV concepts will always be greatly delayed by the need for technology-and location-specific field testing [12]; these tests are expensive and time-consuming, and the information gathered is irrelevant for other technologies.…”

“…Here, it is applied to predict the performance of c-Si modules, which can be directly comparison with solar field data [12]. Time (year) 10 11 Among all the intrinsic degradation modes, we chose to focus on corrosion, shunting, and delamination because (i) they affect c-Si and thin-film technologies, (ii) substantial field data is available (e.g., from DOE regional test facilities), (iii) our previous success in modeling the related problem of shadow degradation using an end-to-end framework [15], and (iv) most important, a novel accelerated lifetime test for PV technology would dramatically increase overall PV energy output.…”

“…We will investigate three of these phenomena in detail, pursuant to the overall goal of our work, which is to develop a physics-based reliability model to make testable predictions. Ultimately, this approach has potential to: (i) redefine scientific basis of related test standards (e.g., IEC 61215 [3] and 61646 [2]), (ii) improve correlations between test methodologies and field data [12], and (iii) based on end-to-end modeling [13][14][15], predict the reliability of a technology to be installed at a given location.…”

Shutter Technique for Noninvasive Individual Cell Characterization in Sealed CPV Modules

“…Various shading techniques have been used to extract individual cell degradation factors for silicon flat panels, but these required either the removal of the bypass diode [4] (compromising the nondestructive test) or the employment of partial shading to avoid voltage shunts [5]. Bypass diodes protect Fig.…”

Real-Time Parameter Estimation for PV Modules using a Polymer Dispersed Liquid Crystal Active Shading Screen

“…The PDLC light modulation uses pure scattering, not absorption, which has the advantage that all wavelengths of incident light are scattered with a very uniform spectral response. Further details of the use of PDLC to characterize cells under uniform illumination conditions can be found in [1].…”