| Keywords |
Photosensor-based dimming; Office; Simulation; Control algorithms; Target illuminance; Sensitivity; Global illuminance |
| Abstract |
This study discusses the system performances of photosensor-based dimming controls in a small office with a lightshelf. Computer simulations using the Lightscape software were conducted for a variety of daylight conditions.
Four control algorithms were employed, and partially-shielded and unshielded photosensors were used to predict dimming levels. Results indicate that control algorithms containing constant and power functions caused excessive dimming and failed to achieve target illuminance under all sky conditions. A linear algorithm showing relatively insensitive dimming levels to photosensor illuminance was appropriate to achieve the optimum system performance under clear sky, when the photosensor was partially-shielded. In this case, the lighting energy savings ranged from 33.3 % to 74.5 %. The system performance of dimming control based on the four algorithms under overcast sky provided excessive dimming and led to failures of controls. The unshielded photosensors failed to provide the target illuminance under the majority of conditions. The linear regression models between the outdoor global daylight illuminance and photosensor illuminance due to daylight were statistically meaningful with strong correlations. |