Photopic illuminance-based black-box model for regulation of human circadian rhythm via daylight control

Abstract

This paper proposes a methodology to derive a black-box model that can predict equivalent melanopic lux (EML) using photopic illuminance as the input. Using this black-box model, we change only the algorithms for existing buildings equipped with controlled lighting based on photopic illuminance. This enables daylight control to satisfy the required EML criterion for humans. Variables in the DELight and split flux algorithms were utilized in the black-box model, and the relationship between the window position and measurement point was set as the main variable. To derive the black-box model, eight of the user's visual orientations (45° intervals) were determined, and eight expressions corresponding to each orientation were derived. A simulation-based validation of the black-box model revealed that 91.12% of all the timeslots satisfied the threshold EML value (200 EML). This value is significantly higher than that observed when lighting control was performed based on a work-plane illuminance of 500 lx (70.5%). The proposed black-box model can satisfy the criterion for sufficient light to reset the circadian rhythm of humans using existing daylight control systems. This study thus presents a method to apply the concept of circadian rhythm for economical and accessible lighting control in buildings.