Daylighting performance of optical rods

Abstract

A novel tubular daylighting device, the light rod, is shown to have high transmittance throughout the day in Singapore. Constructed of an optical quality polymer and clad by air, the light rod is intended for use in buildings where fabric constraints prevent the use of larger daylighting devices. Maximum measured output is around 360 lm per rod and peak output is expected to be around 400 lm. Bending of light rods by up to 90° to accommodate corners is found to reduce output by less than 20% and modification of light emission is straightforward and aesthetically pleasing. An equation is used to describe light rod transmittance and used to predict performance at high aspect ratios, which is found to far exceed transmittance by light pipes of similar aspect ratio. Light rods of small diameter are expected to transmit light effectively at lengths greater than 4 m. The compact size of the light rods is expected to allow installation in locations previously without access to natural light.