Estimation Performance of Horizontal Light Pipes in Deep-Plan Buildings* Case

Abstract
Today, civil constructions constitute most of electrical energy consumption. To reduce the consumption, man has been led to look for renewable sources of energy as a replacement. This is consequence necessitate further studies in this field and related area. One of the options was to utilize daylight during the day hour in place of electrical power, which in turn needed special preparation. Daylighting provides the opportunity for both energy savings and improved visual comfort and Certainly energy savings . With proper integration of a well-designed artificial lighting system, daylighting can offer significant energy savings by reducing a portion of electric lighting load. An extra benefit is the lowering of cooling load due to the reduction in heat gain from electric lamps. In addition to energy savings, daylighting helps create visually pleasing and productive environment for building occupants. Although windows are likely to remain the most common means of admitting daylight into buildings, they have no intrinsic properties to redirection effects, the opening of the building envelope need to be equipped with additional optical devices, either in addition to the windows or even incorporated into them. The resulting combinations of elements are called ‘advanced daylighting systems’. These equipments are designed to redirect sunlight or skylight to areas where it is required, without glare. In the buildings of Tehran, artificial light is considered as the main contributor to the visual environment, even though there is an abundance of daylight during that part of the day known as ‘office hours’. This source of  light could be subjected to more places study to determine proper means for optimum use of that source. This study has aimed to finding and estimating one of advanced systems of utilizing daylight called ‘horizontal light pipe’, to the extent of estimating quality and quantity of illuminance in the office room with a deep plan and any environment like this. Horizontal light pipes designed for sunny and partly sunny skies are a promising solution for supplementing daylight in deep-plan buildings. Light pipes collect and transport sunlight over long distances to the core of a building; which is composed of 4 parts:  reflecting chamber, reflector, diffusing chamber and glazing openings. This system is designed to fit within the ceiling plenum. In this study a logical argument method has been used. For that, Autodesk Ecotect analysis and Radiance simulation software has been used; light pipe has been designed and analyzed in accordance with Tehran solar lighting condition. The study shows an increase in daylight illuminance levels in the bottom half of the room and far from the window aperture (quantity of the illuminance) also  improve the uniformity of the daylighting luminance gradient across the room (quality of the illuminance) under variable solar condition throughout the year, should this system be adapted. In addition, determined the appropriate length of light pipe (9 meter) for more performance in the buildings. Based on simulation results, for uniform distribution of illuminance with better quality across the room, one light pipe is required in every 4 meter.