Daylight-linked synchronized shading operation using simplified model-based control

Abstract

The impact of glass facades and dynamic shading controls on energy use for lighting and air-conditioning should be carefully investigated to determine ways of saving energy while maintaining comfortable conditions for the occupants. Automated control of interior roller shades may result in improved conditions and reduced energy use if advanced algorithms are used, however recent studies have shown that proper control set points are not easily applied in practice. This paper presents details of a simplified model-based shading control using as a variable criterion the “effective daylight” transmitted into the space; shades move to intermediate positions, aiming to maximize daylight utilization while satisfying visual comfort restrictions. Shade properties and control are linked in this approach, with control operation varying depending on the shade optical properties and facade orientation. The method was implemented in full-scale offices and experimental results are presented in terms of daylight metrics, lighting energy use and visual comfort performance. Furthermore, the control strategy was implemented in an integrated lighting model, validated with experimental data, to investigate the annual daylighting performance of perimeter spaces with one or multiple exterior facades. The method is generalized and can be applied to any shading/glazing properties, location, orientation and room configuration, as well as to spaces with multiple exterior facades equipped with roller shades. Overall, this study presents the principle of synchronized control of multiple window shades on different facades (orientations) of commercial buildings. Integrated with efficient lighting and HVAC controls, it can lead to improvement of daylighting conditions and reduced energy use.