Accelerated Damp-Heat Degradation of Single-Cell PV Modules Using Pressure Cooker

• Main Authors: Tung, Chao-Ming, 童兆民
• Other Authors: Yu, Peichen
• Format: Others
• Language: zh-TW
• Published: 2016
• Online Access: http://ndltd.ncl.edu.tw/handle/gwna76

碩士 === 國立交通大學 === 光電工程研究所 === 105 === Damp Heat (DH) test is part of the qualification tests in IEC 61215. The test is done in a climatic chamber that is kept at 85°C and relative humidity (R.H.) of 85%. It can investigate the PV modules’ resistance to temperature and humidity. Recently, due to the progress in manufacturing processes and packaging technology, most of the PV modules can easily pass the DH 1000 test without degradation. It therefore needs to extend test duration up to thousands of hours in order to qualify the module’s capability to withstand long-term temperature and humidity variation. The process becomes very time consuming. As a result, more stringent accelerated aging protocol, such as Pressure Cooker Tests (PCT) has been proposed. With the temperature more than 105 centigrade and 100% relative humidity, the pressure in the chamber is more than 1 atm. It can force moisture to penetrate into the sample, and shorten the testing time. However, PCT has not been used for the PV industry. Therefore, we hope to establish standard testing procedures of PCT for PV modules. In the first part of this work, we study the failure modes of PCT to ensure it is similar to DH. In the second part, we modified the Peck model, and use this model to evaluate the PV module performance under different environment conditions. Because the PCT in the past is used on IC package test, the size of PCT chamber is not big enough for PV modules. We have to make single-cell PV modules instead. Unlike regular solar modules, single-cell PV modules do not include the Al frame. We therefore replace it by the Al foil. After preparation, the samples are aged in different environments. We study the failure mechanism of samples using IV test, Electroluminescence (EL) and Photoluminescence (PL) images, scanning electron microscope (SEM), and Energy-dispersive X-ray spectroscopy (EDX). We found that the failure mechanism of PCT is due to the formation of silver oxide, enhanced by the high temperature, humidity and acetic acid. Acetic acid is produced by EVA at high temperature and humidity. The formation of silver oxide impedes the electron collection, leading to power degradation. Similar failure mechanism has also been found in the DH test. Besides, our result suggests the 121 centigrade condition of the PCT test is most appropriate to test the reliability of modules. Furthermore, by modifying the Peck model, we can describe the power degradation curves induced by the DH and PCTs successfully. The modified Peck model suggests the degradation rate of PCT 121 is 14.8 times faster than the DH degradation rate.