Monitoring of a light-pipe system

Natural light is an important element in visual comfort and it sometimes influences the quality of vision. The effect of daylight on the human biological cycles and possible physiological alterations in the absence of natural light during the day are well-known. When visual comfort is not completely satisfied, the application of daylight transportation systems in buildings is relevant. Research on and observation of human behaviour and the biological effects of light have shown the vital role of artificial or natural light, in maintaining the physiological and psychological balance in human organisms. When visual comfort is not completely satisfied the constant use of artificial light cannot give a temporal reference, so a careful design of the building as well as the use of a specific daylight component (to control, capture and distribute daylight) that contributes to maintaining the natural light changes in intensity and colour temperature is necessary.Several prototypes have been developed and experience has been obtained in daylight collection and transportation; for example, the light-pipes that represent simple systems to capture and transport the natural light inside a room. Light-pipes (such as tubular light) are simple structures that allow the transmission of daylight from the outside to the inside of a room. They are realized with a top collector (often just a polycarbonate hemispheric dome), the pipe itself, and an emitter. Light-pipes have different designs and they are constantly being improved and updated. The pipes that we intend to analyse have a reflective aluminium sheet with a reflectance of about 99% that transmits the light through multiple specular reflections and that makes the light-pipe increasingly efficient.This paper presents the results of monitoring a light-pipe located inside a windowless laboratory of about 9 m2. The system has been monitored with a luxmeter to evaluate the distribution of the illuminance on a working-plane from January 2005 to June 2006. The indoor and outdoor illuminance and the internal/external illuminance ratio are shown in the graphs.