Performance Evaluation of Photovoltaic Modules by Combined Damp Heat and Temperature Cycle Test

Hyeonwook Park,Woo Kyoung Kim,Wonshoup So

doi:10.3390/en14113328

Abstract

Standard damp heat (DH), temperature cycle (TC), and combined DH-TC tests were performed using monocrystalline Si 72-cell modules with a conventional ethylene vinyl acetate (EVA) encapsulant, and their module performance and electroluminescence images were investigated. During the DH test, a significant drop (~20%) in the maximum output power of the module was noticed, primarily because of the degradation of fill factor and an increase in series resistance at 5500 h of DH testing (DH5500), presumably due to the corrosion of metal electrodes by moisture ingress. Conversely, it was revealed that temperature cycling did not seriously degrade module performance until 1400 cycles. However, the combined DH5000-TC600 test suggested in this study, with a sequence of DH1000-TC200-DH1000-TC200-DH1000-TC200-DH2000, was confirmed to provide harsher conditions than the DH-only test by causing a 20% decrease in maximum output power (Pmax) after DH3000/TC400. Promisingly, we confirmed that the module with a polyolefin elastomer encapsulant showed better durability than the module with EVA even in the combined DH-TC test, showing a limited decrease in Pmax (~10%) even after the DH5500/TC600 test.

Highlights

IntroductionThe module certification process following the International Electrotechnical Commission (IEC) standards (e.g., IEC 61215) adopts accelerated testing methods, such as temperature cycle (TC) and damp heat (DH) tests
During the damp heat (DH) test, the critical drop in the maximum output power of the module was primarily accelerated by the degradation of fill factor (FF) and an increase in Rs, which was mainly related to the corrosion of metal electrodes due to moisture ingress, and later followed by Isc loss after DH6000
It was confirmed that the temperature cycle (TC) test between

Summary

Introduction

The module certification process following the International Electrotechnical Commission (IEC) standards (e.g., IEC 61215) adopts accelerated testing methods, such as temperature cycle (TC) and damp heat (DH) tests. According to IEC 61215 (ed.2), the TC test of PV modules is designed to follow a temperature change between −40 and +85 ◦ C for a pre-set number of cycles, for example, 200 cycles for the TC200 test. Repeated cycles of extreme temperature variation may cause thermo-mechanical stress and damage to components and their interfaces within PV modules, such as cells, metal grids, bus-bars, encapsulant, cover glass, and back-sheets, due to the mismatch in coefficients of thermal expansion (CTE). Electroluminescence (EL) images are taken both before and after TC tests, and their comparison is used to identify possible thermo-mechanical damages, including micro-cracks within cells and delamination between constituent layers [1,2,3]. The interfacial contact failure and breakages between layers within modules can lead to an increase in series resistance, reducing the fill factor (FF) and open-circuit voltages (Voc) [4]

Methods

Results

Conclusion