Comparison of Energy and Visual Comfort Performance of Independent and Integrated Lighting and Daylight Controls Strategies

Automated electric lighting systems and motorized shading systems have been widely used in buildings to minimize lighting and HVAC energy consumption and improve visual comfort. Existing lighting and shading systems typically operate independently, i.e. information is not shared. Although integration of control systems has been proposed to maximize energy efficiency and user comfort these benefits have not been quantified. To address this we performed an in-depth study of one manual, four independent and two integrated control strategies: 1. Manual control of lights and no blinds 2. Independent open-loop blind, closed-loop dimming control 3. Independent open-loop blind, closed-loop dimming control, occupancy and HVAC mode shared with blind system 4. Independent closed-loop blind, closed-loop dimming control 5. Independent closed-loop blind, closed-loop dimming, occupancy and HVAC mode shared with blind system 6. Fully integrated lighting and daylighting control with blind tilt angle control without blind height control 7. Fully integrated lighting and daylighting control with blind tilt angle and height control Simulation results for a reference office building are presented for three climate zones (Baltimore, London, Abu-Dhabi), two types of blinds (interior, exterior) and two window-to-wall ratios (66%, 100%). A dynamic occupancy model was developed from actual office occupancy data and used in the simulations. The results show the breakdown of lighting, heating, and cooling energy consumption. Visual comfort is quantified in terms of ability to maintain illuminance within the desired range and daylight glare index below the acceptable norm. Overall, in most cases, strategy six outperforms all other strategies in energy and visual comfort performance.