- A team of researchers led by Chinese solar manufacturer Trina Solar has developed a novel approach to predict the field degradation from potential induced degradation (PID) for tunnel oxide passivated contacts (TOPCon) double-glass module configuration with double ethylene vinyl acetate (EVA) as an encapsulant.
“The current PV module qualification test standards are insufficient for evaluating the comprehensive impact of actual operating light on the PID effect of PV modules, as PV modules are exposed to both illumination and PID simultaneously in real environments,” the scientists said. “The research on PID testing and the prediction of power degradation in modules under illuminated conditions remains limited.”
The proposed methodology is based on the so-called Arrhenius equation, which is an empirical equation that describes the effect of temperature on the velocity of a chemical reaction. It is the basis of all predictive expressions used for calculating reaction-rate constants.
The academics utilized the equation to fit the power degradation in terms of PID date from steady-state test chamber under illumination.
The experimental setup comprised dual-glass bifacial n-type TOPCon solar modules based on 134 cells measuring 210 mm × 182 mm and manufactured via laser enhanced contact optimization (LECO) technology. The panels relied on 2.0 mm thick soda lime glass and two front and two rear films of commercial EVA with thickness of 0.35 mm.
They conducted the PID tests at China General Certification Center in a test chamber under different damp heat test conditions at 75 C, 85 C, and 95 C, with 800 W/m2 steady-state illumination light source. “To ensure consistent absolute humidity across different temperature conditions, the settings were adjusted to 100% relative humidity at 75 C, 75% relative humidity at 85 C, and 55% relative humidity at 95 C,” they explained, noting that humidity in the test chamber is significantly higher than the humidity of the actual outdoor environment.
The testing included high-temperature conditions of Hainan of China and Saudi Arabia, as well as the high-humidity of offshore photovoltaics. It showed that PID in Hainan can reach 1.57% degradation over a 30-year period, while in Saudi Arabia this value reached 1.13%. As for offshore PV, 30-year PID was estimated at a much higher value of 4.01%.
“The IEC61215:2021 standard incorporates light recovery-based PID, yet many customers remain unaware of the underlying mechanisms,” Trina Solar concluded. “This innovative approach, which facilitates simultaneous PID and light exposure, is more readily embraced by clients. Furthermore, this methodology facilitates the photovoltaic industry’s transition to double-EVA, carrying significant implications for the sector.”
The novel methodology was introduced in the paper “Prediction of potential induced degradation for TOPCon PV modules working in field based on accelerated stress testing,” which was recently published in Solar Energy. The research team included Trina’s CEO Jifan Gao, as well as academics from China’s Nanchang University and Chinese PV glass furnace provider Jiangxi Caihong Photovoltaic Co. Ltd.
Author: Emiliano Bellini
This article was originally published in pv magazine and is republished with permission.
