Wonwook Oh

Evaluation of potential-induced degradation in crystalline Si solar cells using Na fault injection

Abstract Photovoltaic (PV) modules are exposed to high-voltage stress between grounded module frames and solar cells, a configuration called potential-induced degradation (PID). Since PID mainly depends on the solar cells used for module packaging, several steps for PID tests can be omitted. We carried out PID tests on the cell level with Na fault injection in accordance with IEC 62804 and examined the extent of PID with saturation current density (J02) extracted from I–V measurements in the dark. Na-fault injection is a reasonable means for performing PID tests on the cell level without module packaging.

Field degradation prediction of potential induced degradation of the crystalline silicon photovoltaic modules based on accelerated test and climatic data

Abstract We investigated the field degradation modeling of potential-induced degradation (PID) in crystalline silicon photovoltaic modules. Five accelerated tests using four-cell mini modules were conducted to derive the hourly degradation rate of the potential induced degradation. The voltage-Peck model was used for predicting the hourly degradation rate. The field degradation modeling was performed at Busan and Miami. The annual degradation rate in field based on the temperature, humidity, and solar irradiance was calculated as the sum of the hourly degradation rate for one year. The annual degradation rates in Busan and Miami were recorded as 6.93% and 11.23% under 72cells and 18 modules series-connected string configuration, respectively. The annual degradation rate induced by PID in the solar power plant in Busan showed similar result to 8.8%.

Migration of Sn and Pb from Solder Ribbon onto Ag Fingers in Field-Aged Silicon Photovoltaic Modules

We investigated the migration of Sn and Pb onto the Ag fingers of crystalline Si solar cells in photovoltaic modules aged in field for 6 years. Layers of Sn and Pb were found on the Ag fingers down to the edge of the solar cells. This phenomenon is not observed in a standard acceleration test condition for PV modules. In contrast to the acceleration test conditions, field aging subjects the PV modules to solar irradiation and moisture condensation at the interface between the solar cells and the encapsulant. The solder ribbon releases Sn and Pb via repeated galvanic corrosion and the Sn and Pb precipitate on Ag fingers due to the light-induced plating under solar irradiation.

Initial detection of potential-induced degradation using dark I–V characteristics of crystalline silicon photovoltaic modules in the outdoors

Abstract We have studied a method to diagnose the initial potential-induced degradation (PID) of p-type crystalline silicon photovoltaic (PV) modules using the dark I–V (DIV) characteristics of the PV power system. The DIV characteristic behavior is expressed as the reverse saturation current density ratio calculated by the double diode model and the current ratio by comparing DIV and light I–V (LIV) before and after the occurrence of PID of solar cells. The ratio of the normalized maximum power of the PV modules that suffered the initial PID in the outdoors was verified to be 0.0125 RMSE (root mean square error). The proposed method can detect the occurrence of PID by periodically measuring both end PV modules of the same PV string, without interruption of the power plant in the dark state, and it is possible to easily and quickly diagnose the power loss due to the initial PID.

Performance Analysis of Photovoltaic Power System in Saudi Arabia

We have analyzed the performance of 58 kWp photovoltaic (PV) power systems installed in Jeddah, Saudi Arabia. Performance ratio (PR) of 3 PV systems with 3 desert-type PV modules using monitoring data for 1 year showed 85.5% on average. Annual degradation rate of 5 individual modules achieved 0.26%, the regression model using monitoring data for the specified interval of one year showed 0.22%. Root mean square error (RMSE) of 6 big data analysis models for power output prediction in May 2016 was analyzed 2.94% using a support vector regression model.

결정질 실리콘 및 CuInxGa(1-x)Se2 모듈의 부분음영에 따른 태양전지 특성 변화 및 바이패스 다이오드의 작동 메커니즘 분석

This paper presents the impact of partial shading on CuInxGa(1-x)Se2(CIGS) photovoltaic(PV) modules with bypass diodes. When the CIGS PV modules were partially shaded, the modules were under conditions of partial reverse bias. We investigated the characterization of the bypass diode and solar cell properties of the CIGS PV modules when these was partially shaded, comparing the results with those for a crystalline silicon module. In crystalline silicon modules, the bypass diode was operated at a partial shade modules of 1.67 % shading. This protected the crystalline silicon module from hot spot damage. In CIGS thin film modules, on the other hand, the bypass diode was not operated before 20 % shading. This caused damage because of hotspots, which occurred as wormlike defects in the CIGS thin film module. Moreover, the bypass diode adapted to the CIGS thin film module was operated fully at 60 % shading, while the CIGS thin film module was not operated under these conditions. It is known that the bypass diode adapted to the CIGS thin film module operated more slowly than that of the crystalline silicon module; this bypass diode also failed to protect the module from damage. This was because of the reverse saturation current of the CIGS thin film, 1.99 × 10 �5 A/cm 2 , which was higher than that of crystalline silicon, 8.11 × 10 �7 A/cm 2 .

결정질 실리콘 태양전지 모듈의 Potential Induced Degradation(PID) 현상

The use of solar energy generation is steadily increasing, and photovoltaic modules are connected in series to generate higher voltage and power. However, solar panels are exposed to high-voltage stress (up to several hundreds of volts) between grounded module frames and the solar cells. Frequent high-voltage stress causes a power-drop in the modules, and this kind of degradation is called potential induced degradation (PID). Due to PID, a significant loss of power and performance has been reported in recent years. Many groups have suggested how to prevent or reduce PID, and have tried to determine the origin and mechanism of PID. Even so, the mechanism of PID is still unclear. This paper is focused on understanding the PID of crystalline-silicon solar cells and modules. A background for PID, as well as overviews of research on factors accelerating PID, mechanisms involving sodium ions, PID test methods, and possible solutions to the problem of PID, are covered in this paper.