Automated blind control based on glare prevention with dimmable light in open-plan offices

This paper presents a simulation study of the control of automated venetian blinds for open-plan office spaces. It has been reported that a cut-off strategy in which the slat angle of the blind is determined to cut direct sunlight is not sufficient to avoid glare. Therefore, in this study, a glare prevention control is proposed whereby the slat angle is repeatedly altered until the glare degree is calculated to be less than the glare index limit. To predict glare degree, a metric that we developed, known as PGSV (Predicted Glare Sensation Vote), is used. To obtain PGSV, the average luminance of the window area including blind slats and the outside view seen between the slats is calculated. For electric lighting control, this study focuses on daylight reflected on the ceiling, which can reduce the required amount of light from electric lighting. The illuminance of the ceiling surface provided by light from the window areas is calculated. This electric light control integrated with blind control requires input from rooftop sensors, without need for indoor photo-sensors. It is suitable for offices using partitions that block light from the windows. The glare prevention method proposed in this paper shows greater slat angle than that in the cut-off strategy. However, it can reduce power consumption for lighting by approximately 30% in typical open-plan offices in Tokyo. Moreover, it provides 46-50% of view satisfaction, which is the percentage of working hours when the occupants are satisfied with the outside view.