Tubular Light Guides: Estimation of Indoor Illuminance Levels

AbstractTubular light guides are novel technology means to achieve energy savings in windowless interiors in the core of buildings and their design and evaluation posed a considerable challenge to illuminating engineers due to task complexity. The Hollow Light Guide Interior Illumination Method – HOLIGILM presented analytical calculations predetermining the illuminance distribution on the interior working plane as well as on the top of the interior tubular diffuser. This precise mathematically defined daylight transport taking into account both sun and sky luminance, tube size as well as cupola and inner diffuser transmittance is derived from basic relations and backward ray-tracing procedures and expressed in complex formulae and a developed computer program HOLIGILM 4.2 for quick calculations of the exact interior illuminance distribution. This program was used to calculate interior illuminance and document with examples modeled indoor illuminance distribution considering standard daylight situations an...