Novel daylighting system based on advanced embedded optical microstructures for various facade orientation and climates

The design of highly glazed building has become a worldwide trend in modern architecture. However, glazing may induce large thermal loss in winter while increase cooling load in summer, and it may also cause glare. In order to solve the problems, a novel multifunctional glazing with embedded optical microstructures was proposed. The glazing consists of a polymer layer with embedded optical microstructures, and the polymer layer is laminated with a glass pane of glazing. The proposed glazing is based on the combination of microstructured geometry and optical coating. According to the geometry, two types of optical microstructures were originally developed in this thesis: i) L-shape retro-reflective optical microstructure, and ii) micro compound parabolic concentrators. The developed optical microstructures have the following advantages: i) seasonal thermal dynamics, ii) daylighting, iii) glare protection, iv) clear view, v) avoiding overheat as well as glare on streets, vi) applicable to various façade orientations, vii) no need of alignment during fabrication The work for this thesis was sorted into three categories: simulation to estimate the potential benefits of the proposed glazing, sample fabrication, and experimental characterization. Prior to the fabrication, ray-tracing simulation was used to optimize the geometrical parameters of the microstructures. The angular-dependent transmittance for glazing with various optical microstructures was calculated from ray-tracing simulation. Dynamic solar gains and the direct transmittance as function of working hours were calculated to evaluate the potential benefits. In order to fully explore the potential advantages in daylighting and glare protection, metrics based on illuminance, uniformity, glare and directivity were used for a south-facing façade equipped with the optical microstructures in Lausanne, Switzerland. In order to redirect daylight as desired, high aspect ratio microstructures and microstructures with overhang were needed. However, the fabrication of such microstructures was challenging with the existing technique. The experimental procedures have been conducted to solve the challenges in the master mold fabrication, replications, UV imprinting, thin film deposition and roll-to-roll extrusion process. The present thesis focuses on the feasibility for the fabrication of the mentioned microstructures above, parameter optimization, and the development of novel processing methods. Structural characterization was conducted during the fabrication steps using conventional optical microscopy, confocal microscopy, and scanning electron microscopy (SEM). Concerning optical characterization, goniophotometer was used to evaluate the angular-dependent transmittance and the light-redirectability of the fabricated samples. Spectrometers were also used to obtain the reflectance and transmittance spectrum of the deposited thin films.


Advisor(s):
Scartezzini, Jean-Louis
Schueler, Andreas
Year:
2019
Publisher:
Lausanne, EPFL
Keywords:
Laboratories:
LESO-PB


Note: The status of this file is: EPFL only


 Record created 2019-05-01, last modified 2019-08-05

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