framework. This phenomenon known as Potential Induced Degradation (PID),. Discovered by SOLON and presented at the 25th PVSEC in Valencia in 2010 [1],.
POTENTIAL INDUCED DEGRADATION EFFECT AND REVERSIBILITY FOR CRYSTALLINE BASED PV SYSTEM UNDER OUTDOOR CLIMATE OF MID-SOUTH WESTERN–MOROCCO Abdellatif Bouaichi1,2*, Choukri Messaoudi1 , Aumeur El Amrani1, Aboubakr Benazzouz 2, Abdellah El Hassani El Alaoui2, Zakaria Naimi2, Amin Bennouna3, Badr Ikken2 1OATE Faculty of Sciences and Techniques, P.C 509 Boutalamin 52000, Errachidia, Morocco 2Institut en Energie Solaire et Energies Nouvelles (IRESEN); 6208, Agdal - Rabat, Morocco 3LPSCM Cadi Ayyad University, Marrakesh, Morocco INTRODUCTION
RESULTS AND CONLUSIONS
The analysis of degradation mechanisms of photovoltaic (PV) modules is a key to ensure current lifetime exceeding 25 years. Over the past decade, an inexplicable power loss has been observed resulting from the stress exerted by system voltage bias which remains a major problem in the PV industry. This effect related on the leakage current between PV cells and module frame has been highlighted by NREL since 2005 [1]. Because of the voltage bias degradation is linked to the leakage current passed from the active layer through the encapsulant and glass to the grounded module frame when the insulation between structure and active layers is not perfect, electrons in materials used for PV modules escape via the grounded framework. This phenomenon known as Potential Induced Degradation (PID), Discovered by SOLON and presented at the 25th PVSEC in Valencia in 2010 [1], has received considerable attention in recent years due to its detrimental impact on PV module performance in field conditions. Both crystalline silicon (c-Si) and thinfilm (TF) based PV modules are susceptible to PID. There were studies that PID can reduce the performance of solar panels, but the results were not clearly quantified. This study focuses on the effects of PID on the performance of c-Si based solar PV panel installed on the mid-southwesternMorocco.
M1= (M1): PV module with PID
M2= (M19): PV module after Reverse biased Figure 2: EL images of PID-affected module By comparing the EL images of investigated PV module before and After the reverse biased voltage, the PID defect has been eliminated.
APPROACH investigated PV system consists of a 22.2-kWp monocrystalline based grid connected after almost two years of outdoor exposure. The PV system consists of two PV strings of 19 modules, where the potential of each string is between ±330 V depending on inverter assembly. The frame of the PV modules has, however, a potential of 0 V, since it must be grounded for safety reasons. The investigation has focused on two module (M1 and M19, see Fig below) of one string. The study has been divided into two parts: The output power decrease due to PID will be quantified. On the other hand, PID is one 100% reversible or shows irreversible parts were verified by inversing the inverter polarity.
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PV+
Figure 3: degradation of power before and after PID recovery
b
a
Figure 1: a-Investigated monocrystalline PV modules and b- synoptic view of PV system before reverse biased voltage
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The output power of affected module has been decreased by -10.12% comparing the its initial value.
After reverse biased voltage the output power of the PID-affected module has been improver with 2.43%. Regarding PV module in positive potential, its output power has been decreased to -5.69 comparing to -1.5 before reverse biased. reverse biased voltage can partially improve the output power of the PID affected PV module
Reference: 1. Pingel, S., et al. "Potential induced degradation of solar cells and panels." Photovoltaic Specialists Conference (PVSC), 2010 35th IEEE. IEEE, 2010.
