Engineering topics
Publications and source records attributed to Colvin, Dylan.
We demonstrate a charges transfer from the atmosphere to the modules’ frame in the field and discuss the mechanism - leakage current measured in the field are not only related to the PV module operation - this is crucial to consider in potential-induced degradation modeling
Potential induced degradation (PID) is a reliability issue affecting photovoltaic (PV) modules, mainly when PV strings operate under high voltages in hot/humid conditions. Polarization-type PID (PID-p) has been known to decrease module performance quickly. PID-p can be reduced or recovered under the light in some cases, but this effect, as expected, would be less pronounced on the rear side of bifacial PV modules receiving lower irradiance. As bifacial PV modules are projected to dominate the PV market within the next 10 years, it is crucial to understand the PID-p issue in bifacial modules better. In this study, we performed indoor PID testing to induce PID-p on 14 commercial bifacial p-PERC modules with three different module constructions from three manufacturers. Here, four rounds (+ve and –ve polarities for front and rear sides) of PID testing are done at 25°C, 54% relative humidity (RH) for 168 h using the aluminum foil method. Each module side (front cell side and back cell side) is tested individually under both negative and positive voltage bias. The results show that the highest degradation of 32% in maximum power (Pmax) at standard test conditions (1000 W/m 2 ) and 51% at low irradiance (200 W/m 2 ) has been observed in some cases. Recovery under sunlight is also done, and outcomes show a near-complete recovery in Pmax. This study presents an extensive experimental methodology and a detailed analysis to systematically and simultaneously/sequentially evaluate multiple construction types of bifacial modules to the PID-p susceptibility and recovery.
Bifacial modules are increasingly deployed in the field and are expected to represent half of the market share within 10 years. Their rear structure differs from monofacial modules to allow additional light absorption. However, it brings new reliability challenges to address. In particular, the risk of potential-induced degradation (PID) is increased as both module sides are impacted. Different PID processes have been identified in the literature: shunting type (PID-s), polarization type (PID-p), Na penetration type, and corrosion type (PID-c). Their occurrence depends on the photovoltaic system configuration as well as the module's materials. Apart from PID-s, PID processes are not well understood and extensive research is needed to elucidate the PID scenario and underlying mechanisms. Herein, current knowledge about PID processes and their impact on the main bifacial modules in the market are gathered with the aim to guide future research. Bifacial module technologies and leakage current paths leading to PID are described. Indoor and outdoor PID testing methods are detailed. For each bifacial module technology, the PID processes are investigated with their indicators, mechanism and recovery process. Furthermore, PID-impacting factors and limitation solutions are finally reported and a state of the art on PID modeling is presented.
The market share of silicon heterojunction (SHJ) modules are expected to increase in the following years. The presentation discusses field performance of SHJ and compares it to other high-efficiency modules. In-depth materials characterization is used to understand the origins of degradation in these type of modules.