The effect of cooling press on the encapsulation properties of crystalline photovoltaic modules: residual stress and adhesion

• Published in: Progress in photovoltaics Vol. 23; no. 2; pp. 160 - 169
• Main Authors: Li, Heng-Yu, Perret-Aebi, Laure-Emmanuelle, Chapuis, Valentin, Ballif, Christophe, Luo, Yun
• Format: Journal Article
• Language: English
• Published: Bognor Regis Blackwell Publishing Ltd 01.02.2015; Wiley Subscription Services, Inc
• Subjects: adhesion; Cooling; cooling press; Cooling rate; Encapsulation; Ethylene vinyl acetates; EVA; Glass; Modules; Photovoltaic cells; photovoltaic module; Presses; residual stress; Solar cells
• ISSN: 1062-7995; 1099-159X
• DOI: 10.1002/pip.2409

A high‐quality encapsulation process is crucial to ensuring the performance and long‐term reliability of photovoltaic (PV) modules. In crystalline Si technology‐based modules, poly (ethylene‐co‐vinyl acetate) (EVA) is the most widely used PV encapsulant. Its encapsulation process is usually performed in a flat‐bed vacuum bag laminator. In certain types of laminators, cooling press can be applied to the module cooling process after the module encapsulation, leading to a much higher cooling rate (~100 °C/min) than conventional natural cooling due to the application of water cooling circulation and mechanical pressure on the modules. In this work, the effect of the cooling press on the encapsulation properties of PV modules with EVA as the encapsulant are assessed on the aspects of residual stress in the modules, peeling strength between glass and EVA, and the resulting EVA gel content after encapsulation. The results show that the cooling press influences the encapsulation properties of PV modules. In particular by applying the cooling press after encapsulation, the residual normal stress in the Si solar cell in the encapsulated module after cooling can be reduced by as much as 22 ± 2 to 27 ± 3% depending on the EVA gel content, whereas the peeling strength between front glass and EVA is increased by ~ 10%. This work should help the further optimization of PV module encapsulation processes aimed at improving module encapsulation quality. Copyright © 2013 John Wiley & Sons, Ltd. The effect of the cooling press (CP) on the encapsulation properties of photovoltaic modules with ethylene vinyl acetate (EVA) as the encapsulant is assessed in this work. It is shown that, by applying CP, the residual stress in the encapsulated module after cooling is reduced greatly, whereas the peeling strength between front glass and EVA is enhanced. The EVA gel content remains unaffected by CP, but the high cooling rate clearly hinders the crystallization process of the EVA encapsulant during cooling.