Assessing the Lighting Performance of an Innovative Core Sunlighting System

Abstract

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 5 m and 10 m from the building façade. Photometric measurements throughout a year show that the system can consistently provide more than 300 lx for 9 h (9:00 to 18:00) under clear and partly cloudy skies, and during 4 h under overcast sky conditions (exterior global horizontal illuminance, EXGH, over 18–20 klx). In addition, the illuminance values, over 1000 lx are achieved consistently between 10:30 and 16:30 under clear sky conditions. At the back of the space (7.6 m under the light pipe), the Useful Daylight Illuminance autonomous (UDI-a, 300–3000 lx), UDI autonomous for aging eyes (UDI-a AE, 600–3000 lx) and UDI-a Bright Daylight (BD, 1000–3000 lx) ranged between 60–88%, 44–64%, and 28–45% respectively. The light pipe introduces consistently illuminance levels ranging between 300 lx and 2500 lx throughout the year, saving energy during peak load electricity demand, and providing the daily bright light doses necessary to regulate and entrain building occupant’s circadian rhythms.

This passive solar system proves to be an energy efficient sustainable technology that utilizes direct solar energy, and provides high illuminance levels of full-spectrum light without the negative effects of glare and solar heat gains that are found in buildings with large expanses of glass.