Thesis-2015-Rashtchi.pdf (140.64 MB)
Non-contact techniques for measuring moisture related properties of Ethylene Vinyl Acetate as a photovoltaic module encapsulant
thesis
posted on 2015-10-20, 08:49 authored by Shabnam RashtchiPolymer based encapsulant materials such as Ethylene Vinyl Acetate (EVA) are commonly used in silicon-based PV modules and play a central role in the structural integrity
and hence long term performance of the device. In spite of many advantages, however,
water can di!use through them, leading to swelling and chemical degradation that can
make the device susceptible to accelerated corrosion and failure. This thesis reports on
e!orts to provide novel methodologies to investigate the opto-mechanical response of
EVA due to water di!usion and on the quantification of water concentration in deployed
PV modules. A novel non-contact time-resolved measurement technique based on Wavelength Scanning Interferometry (WSI) is proposed to determine thickness, refractive index, thickness change and refractive index change in EVA during water uptake. This is
preceded by numerical simulations to inform the design of the experimental methodology
and setup, such as thickness of EVA layer, maximum surface velocity during measurements, type of data filters to use for data analysis and also for validating the proposed
approach. The measured time-resolved thickness profiles provide a unique opportunity
to study the swelling behaviour of EVA. Using a novel inversion technique, the hygroscopic expansion coe"cient (HEC) as a function of water concentration is established
for the first time. A hygro-mechanical Finite Element model is also developed to predict
time-resolved hygroscopic expansion of EVA and compare it with experimental measurements. The hygro-mechanical stress is further studied through a set of deflection tests on
EVA-glass bi-material strip specimens immersed in water and intermittently measured
with an optical profilometer.
Funding
EPSCR, STAPP, Loughborough University
History
School
- Mechanical, Electrical and Manufacturing Engineering
Publisher
© Shabnam RashtchiPublisher statement
This work is made available according to the conditions of the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0) licence. Full details of this licence are available at: https://creativecommons.org/licenses/by-nc-nd/4.0/Publication date
2015Notes
A Doctoral Thesis. Submitted in partial fulfilment of the requirements for the award of Doctor of Philosophy of Loughborough University.Language
- en