Optical transmission as a fast and non‐destructive tool for determination of ethylene‐co‐vinyl acetate curing state in photovoltaic modules

Abstract

Poly(ethylene‐co‐vinyl acetate) (EVA) is the primary polymer used for encapsulation of photovoltaic (PV) modules. Its degree of cross‐linking (gel content) is taken as a major quality reference. The EVA gel content is normally measured by Soxhlet extraction and more recently also by Differential Scanning Calorimetry (DSC). The DSC method is proven here to be fast and effective but is, as the Soxhlet extraction method, destructive to the PV module. With the aim of developing a fast and non‐destructive method to determine the gel content, a number of analytical techniques are presented. The most promising method is ultraviolet/visible/near‐infrared (UV/Vis/NIR) optical transmission. The measured diffuse transmission reflects the EVA crystallite size, which is related to the EVA gel content. This opens the possibility to apply an in‐line analysis of every PV module immediately after the lamination step and could significantly contribute to the process quality control that is needed in future high‐throughput production lines of PV modules. Copyright © 2011 John Wiley & Sons, Ltd.

Effect of Cooling Press on the Optical Transmission Through Photovoltaic Encapsulants

“…As has been shown in Ref. [10] , the change of the crystallinity of encapsulants will be reflected in the optical transmission through them. Therefore, in this work, we intend to study the effect of CP on the optical transmission through several types of PV encapsulants and explore its potential application on improving their optical properties.…”

Fast and Nondestructive Detection on the EVA Gel Content in Photovoltaic Modules by Optical Reflection

“…The optical detection in transmission mode on the EVA gel content in PV modules has been well documented in [17]. However, the optical detection in transmission mode only works for transparent PV modules.…”

“…A few of them such as DSC and DMA remain to be destructive, although they can shorten time required per measurement. Previously, a fast and nondestructive approach for detecting the EVA gel content has been reported by our group, based on the UV/Vis spectroscopy [17]. The limitation of this development is that it relies on the optical transmission measurement and, hence, can only be applied onto transparent modules.…”

Contact-free Determination of Ethylene Vinyl Acetate Crosslinking in PV Modules with Fluorescence Emission

“…These methods are also all destructive, as they require a sample of material from the module. Some non-destructive alternative techniques have been developed, relying on the sound velocity in the material [2], the change of dielectric properties of EVA during crosslinking [3], the diffusion of visible light in transmission [4] through glass-glass modules, or the measurement of stiffness through the backsheet with an indenter [5]. These methods can either not be used in-line, require the insertion of a supplementary device in the module or are constraining the module design.…”