Bended Light-Guide Modeling Under Broken Cloud Arrays

Bended light-guides represent an effective way of transporting of daylight into interiors of buildings, which can not be illuminated by vertical or roof windows. The effectivity of using those kind of devices depends on their physical parameters (length, diameter, band orientation, inner reflectance). But dependence on exterior properties, such as position of Sun, turbidity of atmosphere and mainly the presence of broken cloud arrays, is prior. Experimental approach of describing behavior of a light-guide is practically impossible, because of rapid changes of exterior conditions and of unrepeatability of measurements. Therefore, there is a need of numerical modeling as accurate as possible, which takes into account a wide range of sky states and variable configuration of light-guide. So far, most of such modeling were based on using empirical models, while our approach includes local state of the atmosphere and also 3D modeling of light transport through the light-guide. This contribution is focused on determining the efficiency of the bended light-guides with different bend angles and orientation of their upper part by various levels of cloud fractions and positions of Sun. As a modeling tool, a link between the programs Unisky Simulator and Holigilm was created. Unisky Simulator is designed to model sky luminance distributions for arbitrary meteorological conditions and Holigilm enables calculations of light transmittance bended light-guides.