Using of light guides (light tubes) for illumination of rooms becomes very popular method. The sunlight is captured by a cupole (located usually on the roof) and guided through hollow reflective guide into the room. At the end of the guide an optical interface (usually a diffuser) is placed, which scatters the light into whole room. A schematic drawing of a typical light guide is shown in the picture located on the top left of this page.
The calculation of the illumination using light guides is quite complicated task, which includes entering of the light through the cupole, multiple reflecting of the light inside the tube and the scattering of captured light in the optical interface. "Classical" method for such calculations is Monte-Carlo method combined with ray-tracing. This method requires huge long-time calculations. The main advantage of the HOLIGILM is, that it is based on analytical solution of the problem described in the scientific paper published in Solar Energy 82 (2008) 247-259. Thanks to this sophisticated method is HOLIGILM extremly fast. The time needed to obtain accuracy comparable with Monte-Carlo methods is dramatically lower and is typically less than one minute on a standard PC.
HOLIGILM is freeware - you can use it without functional or time limitations. However, in the case you found it useful and you will publish results based on HOLIGILM calculations, we ask you to refer our paper(s).
HOLIGILM has user-friendly GUI (Graphical User Interface)! Set parameters of the room, ligh-tubes etc. in dialogs. View results in GNUplot window and save quality plots: