An experimental and analytical study of transmission of daylight through circular light pipes

This paper presents results of modeling, experiments, and simulation of transmission of beam and diffuse daylight through straight circular light pipes with and without bends. Analytic method is used in the development of an algorithm for tracing light rays that enter, are reflected from interior pipe surfaces, and eventually transmit from a pipe. Each bend section is modeled as a torus. For short straight pipes, the transmitted collimated rays at the exit ports form interesting geometrical patterns. Results from calculation of transmission of beam and diffuse daylight through straight pipes with and without bends match well with results from experiments. The paper also compares results from calculation of transmitted daylight illuminance when measured luminance of 145 standard sky zones are used to form entering rays, and when generated luminance of the same sky zones are used. The method presented is theoretical but lends itself to practical application. © 2011 The Illuminating Engineering Society of North America.