Non-contact monitoring of soda-lime glass surface changes by its LWIR apparent emissivity: Possibilities and limitations - Université Paris-Est-Créteil-Val-de-Marne Access content directly
Journal Articles NDT & E International Year : 2023

Non-contact monitoring of soda-lime glass surface changes by its LWIR apparent emissivity: Possibilities and limitations

Abstract

Soda-lime glass is widely used in many areas of daily life because of it is inexpensive, chemically stable, reasonably hard, extremely workable, and has excellent optical properties. In use, it is subject to weathering degradation. This causes surface changes that reduce its optical properties. After carrying out a spectral characterization of their effects, we highlight that the changes produced have a specific signature in the LWIR band due to the IR absorbing properties of the glass. Therefore, LWIR cameras used as radiometers are perfectly suited for their quantification by a non-contact measurement of their LWIR apparent emissivity. The LWIR apparent emissivity is provided in a quantitative thermographic approach. Based on the imaging capabilities of the thermal camera, it is possible to generate a 2D mapping of the surface changes in the form of an emissogram. The metrological capabilities of LWIR bolometric thermal cameras are then tested under laboratory conditions (strict control of influence temperatures) and under outdoor conditions. Under laboratory conditions, LWIR apparent emissivity is capable of quantifying anomalies as small as A=5%µm. The indicator is suitable for managing the effects of erosion and hydration of glass, respectively from 8 % of the eroded surface and from 100h of humid heat (2 years of natural exposure in a temperate climate). In outdoor conditions, the reflected temperature is an advantage because it improves the Type B accuracy of LWIR apparent emissivity measurements. Assuming a 3 °C non-uniformity of surface temperature, as it is the case for PV systems with active cooling, we conclude that erosion effects should be quantifiable from 48 % of the eroded surface, allowing optical transmittance losses of glass to be detected from 10 %. The effects of glass hydration remain difficult to manage due to the weakness of the spectral anomalies they produce.
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Dates and versions

hal-04319689 , version 1 (03-12-2023)

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Olivier Riou, Samy Brazane, Fabien Delaleux, Laurent Ibos, Jean-Félix Durastanti. Non-contact monitoring of soda-lime glass surface changes by its LWIR apparent emissivity: Possibilities and limitations. NDT & E International, 2023, pp.102998. ⟨10.1016/j.ndteint.2023.102998⟩. ⟨hal-04319689⟩

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