Nochang Park

Estimation of the degradation rate of multi-crystalline silicon photovoltaic module under thermal cycling stress

Abstract The overall power of an outdoor-exposed photovoltaic (PV) module decreases as a result of thermal cycling (TC) stress, due to the formation of cracks between the solder and metal. In this study, the thermal fatigue life of solder (62Sn36Pb2Ag) interconnection between copper and silver metallization in PV module was studied. This paper describes in detail the degradation rate ( R D ) prediction model of solder interconnection for crystalline PV module. The R D prediction model is developed which based on published constitutive equations for solder and TC test results on actual PV module. The finite element method was employed to study the creep strain energy density of solder interconnections in TC conditions. Three types of accelerated tests were conducted to determine the prediction model parameters. R D in benchmark condition is predicted and compared with those of TC conditions.

Study on Mitigation Method of Solder Corrosion for Crystalline Silicon Photovoltaic Modules

The corrosion of 62Sn36Pb2Ag solder connections poses serious difficulties for outdoor-exposed photovoltaic (PV) modules, as connection degradation contributes to the increase in series resistance () of PV modules. In this study, we investigated a corrosion mitigation method based on the corrosion mechanism. The effect of added sacrificial metal on the reliability of PV modules was evaluated using the oxidation-reduction (redox) reaction under damp heat (DH) conditions. Experimental results after exposure to DH show that the main reason for the decrease in power was a drop in the module’s fill factor. This drop was attributed to the increase of . The drop in output power of the PV module without added sacrificial metal is greater than that of the sample with sacrificial metal. Electroluminescence and current-voltage mapping analysis also show that the PV module with sacrificial metal experienced less degradation than the sample without sacrificial metal.

Field discoloration analysis and UV/temperature accelerated degradation test of EVA for PV

For more than 25 years of lifetime of Photovoltaic (PV) module, the importance of the study about the durability of PV module component is getting higher and higher. Ethylene Vinyl Acetate (EVA), Polymer encapsulation, is one of the important components to protect the cell and improve optical transmittance. Therefore, the study about improving the durability through long term degradation characteristic of E VA based on the environmental stress is essential. This study investigates discoloration degradation mechanism of E VA under Ultraviolet (UV) and temperature complex environmental stress. Chemical/physical change of 25 year-old EVA years was analyzed. Similar amount of UV/Temp acceleration condition which was induced to E VA for 25 years design. After Acceleration Degradation Test (ADT), degradation characteristics were analyzed by using SEM, FT-IR, TGA, and DSC. The result was compared with field-aged EVA.

The effect of encapsulant delamination on electrical performance of PV module

This paper focuses on the effect of delamination on electrical performance in PV module, especially electrical loss of solar cell. Degradation mode of field aged crystalline-Si PV module has been investigated through visual microscope. Electrical performance was measured with solar simulator. Electroluminescence analysis was carried out for detecting defects of PV module. Delamination observed in the PV module has occurred at the interface between the encapsulant and the front surface of the solar cell and between the encapsulant and glass. Delamination was a main degradation mode of PV module. To describe the effect of delamination on the electrical performance, new analysis through line irradiance system for electrical mapping was used. Investigation of delamination indicated that new analysis is useful to describe the effect of delamination compared to the electroluminescence analysis.

Analysis for the degradation mechanism of photovoltaic ribbon wire under thermal cycling

For assurance more than 25 year lifetime of photovoltaic module, the reliability of components and material should be guaranteed. This study draws a conclusion of ribbon wire degradation mechanism among the materials under thermal cycling. The main degradation mechanism of ribbon wire the crack caused by coefficient of thermal expansion (CTE) mismatch between the module material and the ribbon wire solder. To demonstrate the degradation mechanism, thermal cycle test was designed and conducted with small photovoltaic module. The temperature cycle condition was (−) 45°C ∼ (+) 85°C and the dwell time was 20 minutes. Measurement was carried out every 100 cycles monitoring the series resistance (Rs) through dark I-V. The result shows that Rs increases. After 1,000 cycles, the characteristics of Dark I-V and illuminated I-V were compared and analyzed. Failure mechanism analysis was conducted for the modules which decreased 20 % of Pmax. Water-jet techniques for cross-section and SEM were used to analyze the factor of resistance change and efficiency degradation. The degradation mechanism of ribbon wire was proved.

Lifetime prediction model of thermal fatigue stress on crystalline silicon photovoltaic module

Thermal cycling stress can result in fatigue cracks of interconnections between ribbon wires and the metallization of a photovoltaic (PV) module, thereby increasing its series resistance. Therefore, in this study, the thermal cycling (TC) history of PV modules exposed to two benchmark climate (Phoenix, AZ) has been derived employing corresponding meteorological data. Using the three parameters rain-flow counting algorithm, the number of TCs versus temperature change was calculated over one year. The number of rain-flow cycles was 935 in Phoenix. Furthermore, three types of accelerated tests were conducted to develop a lifetime prediction model. The Basquin equation was used to predict the number of cycles to failure, based on stress calculation. A finite element model for stress analysis was developed. Failure analysis shows that crack occurred at the solder joint after accelerated test.

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.

Advanced Yield Strength of Interconnector Ribbon for Photovoltaic Module Using Crystallographic Texture Control

This paper reports a study on reducing the yield strength of Cu ribbon wire used for Si solar cell interconnections in solar panels. Low yield strength Cu core should be used as the interconnector ribbon to minimize the fracture of Si solar cells during the tabbing process. We lowered the yield strength of Cu ribbon by controlling the crystallographic texture without increasing the annealing time and temperature. The crystallographic texture was controlled by lubrication in a cold rolling process. The crystallographic texture was observed by scanning electron microscopy with electron back scattered diffraction. A tensile test was performed for the comparison of the mechanical properties of Cu with and without lubrication. The average yield strength was 91.2 MPa with lubrication whereas the yield strength was 99.6 MPa without lubrication. The lower value of the lubricated samples seemed to be caused by the higher cube texture intensity than that of the samples without lubrication.

Analysis of semiconductor fault using DS (damped sinusoidal) HPEM injection

Electronic systems based on solid state devices have changed to be more complicated and miniaturized as the systems developed. The evaluation of HPEM (High Power Electromagnetics) has been mainly carried out in the system level, and the case of failure analysis on the device is very rare. If the electronic components (semiconductor) are exposed to HPEM, the semiconductor will be destroyed by the coupling effects of electromagnetic waves. Because the HPEM has fast rise time and high voltage of the pulse, the semiconductor is vulnerable to external stress factor such as the coupled electromagnetic pulse. By injecting Damped Sinusoidal Pulse to the semiconductor devices, were observed the increase of leakage current and the physical damage.