Lawrence Berkeley National Laboratory

Automated daylight redirecting slat technologies are designed to divert sunlight into the living space. They have a distinct advantage in that they can be retracted and extended, and slat angles can be adjusted according to the solar geometry and sky conditions. This study aimed to explore the geometric and photometric properties of a novel high-efficiency light redirection system (LRS). The LRS prototypes were installed in the clerestory window in the south-facing window testbed office and monitored under real sun and sky conditions. Workplane illuminance, daylight delivery efficiency (DDE) and visual comfort were evaluated. A number of simulation studies were conducted to evaluate the LRS and compare the results to the laboratory tests. The study shows that the specular properties of the slats provided significantly higher work plane illuminance and DDE. All systems showed an acceptable discomfort glare, or daylight glare probability (DGP) lower than 0.35. The comparison of the laboratory test and computer simulation was conducted using a Radiance tool. The results show that, for specular slats, the mkillum method with plastic material provided accurate work plane illuminance compared to the measurement. All simulated DGP shows accurate results compared to the laboratory test.