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Jing Gong receives PhD for microstructured glazing

Andreas Schueler & Jing Gong © Alina Walch 2019 EPFL

Andreas Schueler & Jing Gong © Alina Walch 2019 EPFL

Jing Gong has received a PhD for her work on a novel daylighting system based on advanced embedded optical microstructures for various facade orientations and climates. The microstructured glazing addresses the glare and overheating issues often encountered in buildings with glazed façades, and aims to improve solar gains in winter.

The design of highly glazed buildings has become a worldwide trend in modern architecture. However, glazing may induce large thermal losses in winter while increasing cooling load in summer, and it may also cause glare. In order to solve these 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 developed in 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.

Related to this thesis, in December 2018, Jing Gong and her co-authors received the best paper award in non-imaging optics for their paper Feasibility study on a novel daylighting system with embedded micro compound parabolic concentrators (CPCs), presented at the SPIE Optical Engineering & Applications Conference of 19-20 August 2018, in San Diego, CA, USA

Jing Gong's thesis was supervised by Dr Andreas Schueler and Prof. Jean-Louis Scartezzini.

Funding

This research was funded by the Swiss Innovation Agency Innosuisse through the Swiss Competence Center for Energy Research "Future Energy Efficient Buildings and Districts" SCCER FEEB&D.

References

Gong, Jing; Scartezzini, Jean-Louis; Schueler, Andreas (dirs.), Novel daylighting system based on advanced embedded optical microstructures for various facade orientation and climates, EPFL Thesis no. 9390, 2019


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