Tracing of daylight through circular light pipes with anidolic concentrators

Abstract

Light pipes can bring both daylight from the sun and the sky into deep interior spaces of a building. Adding an anidolic concentrator at the entry port of a light pipe will increase daylight capture and may reduce the overall cost per unit of delivered daylight flux, especially for long pipes or pipes with bends. This paper presents results of modeling, experiments, and simulation of transmission of beam and diffuse daylight through tubular light pipes attached with an anidolic concentrator at the entry port. Analytic method is used for tracing light rays from the sun and sources in the sky zones through the anidolic concentrator to the straight section of a pipe through to the exit port. The vertical curvature surface of the anidolic concentrator is modeled as a parabolic section. The ASRC-CIE sky luminance distribution model is used to generate luminance of daylight from the sky. The algorithms are coded in a MATLAB program. The physical anidolic concentrator and pipe are fabricated from off-the-shelf materials commonly available. The interior surface of each section is lined with a film of reflectance of 99%. Results from calculation of transmission of global and diffuse daylight through the tubular pipe with anidolic concentrator match well with those from experiments.