DIRECTIONALLY SELECTIVE DIELECTRIC STRUCTURES FOR SOLAR-RADIATION CONTROL

Windows represent a primary approach for direct indoor use of solar en ergy in terms of lighting and heating if differentiated radiation cont rol ensures continuous visual and thermal comfort. Total internal refl ection is g well known phenomenon that can fulfil directionally select ive tasks covering most of the solar spectrum without absorption. Prom ising designs of dielectric structures are presented together with per formance results from two-dimensional ray-tracing. Dynamic solar contr ol systems based on rotatable slats can be modified in two ways. The f irst design complements state of the art prismatic structures in order to provide partial transparency of the material itself. A new approac h rearranges the reflective segments in a way that enables total inter nal retro-reflection. The spacing between adjacent slats for unobstruc ted view can be increased for selected solar profile angles. For stati onary solar control, cylindrical shells have been devised that can tot ally reflect a broad range of incoming rays. The new design removes th e constraint on total reflectance aperture angle exhibited by prismati c geometry. Seasonal solar control on vertical southern facades can be achieved with a structure that reflects light only from high elevatio n angles and is partly transparent in other directions. (C) 1998 Elsev ier Science Ltd. All rights reserved.