An experimental setup to evaluate the daylighting performance of an advanced optical light pipe for deep-plan office buildings

Abstract

This research focuses on an advanced optical light pipe daylighting system as a means to deliver natural light at the back of deep-plan office buildings (15ft to 30ft), using optimized geometry and high reflective materials. The light pipe configurations follow a previous study at the Lawrence Berkeley National Laboratory (Beltr??n et al., 1997). The current system is designed for College Station, TX (lat: 30?? 36??N), with predominantly mostly sunny sky conditions. This work consists of the monitoring of two scale models simulating a portion of a multi-story office building with open-plan configuration, with interior dimensions 30ft x 20ft x 10ft, built at 1:4 of its real scale, one of the models being the reference case and the other the test case where the light pipe system is placed. The main objectives of this thesis are (a) to examine this daylighting system comparative to the reference case, taking measurements for longer periods than the study at LBNL, as well as to collect detailed data of its performance under different weather conditions and with different materials; (b) to evaluate the visual comfort and possible glare problems of the light pipe system through photographic evaluation and the conduction of a survey that provides people??s opinions and suggestions about the daylighting system. The light pipe system demonstrated a higher performance than the reference case in terms of appropriate levels of light and people??s preferences. The illuminance at the workplane level showed to be adequate with any of the two different diffusing materials used to spread the light into the room. The light pipe without a diffuser was the other condition observed to further understand the bounces of the sunbeam inside the reflective chamber and its consequences on the lighting output. Recommended standards for office spaces with VDT screens together with the analysis of the daylight system, led to preliminary suggestions on how to integrate the light pipe system in an open-plan office configuration. Further study is indicated to reach the complete potential of this advanced optical light pipe that ties illuminance quality with energy savings through the integration of daylight and electric light systems.