Assessing the Lighting Performance of an Innovative Core Sunlighting System
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This paper presents an efficient daylighting technology to improve the lighting conditions in deep interior spaces of multi-story buildings without the penalties of increased solar heat gains. A passive horizontal solar light pipe is proposed to efficiently redirect sunlight to distances between 5m and 10m from the building faade. Photometric measurements throughout a year show that the system can consistently provide more than 300lx for 9h (9:00 to 18:00) under clear and partly cloudy skies, and during 4h under overcast sky conditions (exterior global horizontal illuminance, EXGH, over 1820 klx). In addition, the illuminance values, over 1000lx are achieved consistently between 10:30 and 16:30 under clear sky conditions. At the back of the space (7.6m under the light pipe), the Useful Daylight Illuminance autonomous (UDI-a, 3003000lx), UDI autonomous for aging eyes (UDI-a AE, 6003000lx) and UDI-a Bright Daylight (BD, 10003000lx) ranged between 6088%, 4464%, and 2845% respectively. The light pipe introduces consistently illuminance levels ranging between 300lx and 2500lx throughout the year, saving energy during peak load electricity demand, and providing the daily bright light doses necessary to regulate and entrain building occupants circadian rhythms.