Embedded microstructures for daylighting and seasonal thermal control

A novel concept for an advanced fenestration system was studied and samples were produced to demonstrate the feasibility. The resulting novel glazing will combine the functions of daylighting, glare protection, and seasonal thermal control. Coated microstructures provide redirection of the incident solar radiation, thus simultaneously reducing glare and projecting daylight deep into the room in the same manner as an anidolic mirror-based system.The solar gains are reduced for chosen angles corresponding to a estival elevations of the sun, thereby minimising heating loads in winter and cooling loads in summer. A ray-tracing program developed especially for the study of laminar structures was used for the optimisation of structures with the above mentioned goals. The chosen solution is based on reflective surfaces embedded in a polymer film that can be combined with a standard doubled glazed window. The fabrication of such structures required several steps. The fabrication of a metallic mould with a relative high aspect ratio and mirror polished surfaces is followed by the production of an intermediate Polydimethylsiloxane moulds that was subsequently used to replicate the structure with a UV curable polymer. Selected facets of these samples were then coated with a thin film of highly reflective material in a physical vapour deposition process. Finally, the structures were filled with the same polymer to integrated the mirrors. The samples were characterised using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), confocal microscopy and laser profilometry. A miniature goniophotometer was built to assess the performance of the structured glazing. The daylighting behaviour was successfully demonstrated.