An advanced lighting system combining solar and an artificial light source for constant illumination and energy saving in buildings

The goal of this work was to develop an active daylighting system where constant illumination is made possible by mixing sunlight and artificial light as needed. A Fresnel lens mounted on a dual axis solar tracker was used to collect sunlight, which was then transmitted by an optical fiber cable. During its transmission, sunlight was mixed with light from an artificial light source (LED lamp, 120 W) to produce a constant flux of light before being discharged into a space. A constant level of illumination was achieved on the task plane throughout the system's operation. This system differs from other active daylighting systems, which require a sensor feedback from some reference point to control the amount of additional light provided to the interior spaces. It is expected that the system will enable solar constant lighting and energy efficiency in indoor illumination to be achieved. Based on a luminous efficacy of 17 lm/W for the LED lamp and operation of 8 h/day for 110 days annually, it is projected that 174 kWh of electric energy could be saved by the present system.