Abstract
In modern society, the average person spends more than 90% of their time indoors. However, despite the growing scientific understanding of the impact of light on biological mechanisms, the existing light in the built environment is designed predominantly to meet visual performance requirements only. Lighting can also be exploited as a means to improve occupant health and well-being through the circadian functions that regulate sleep, mood, and alertness. The benefits of well-lit spaces map across other regularly occupied building types, such as residences and schools, as well as patient rooms in healthcare and assisted-living facilities. Presently, Human Centric Lighting is being offered based on generic insights on population average experiences. In this paper, we suggest a personalized bio-adaptive office lighting system, controlled to emit a lighting recipe tailored to the individual employee. We introduce a new mathematical optimization for lighting schedules that align the 24-h circadian cycle. Our algorithm estimates and optimizes parameters in experimentally validated models of the human circadian pacemaker. Moreover, it constrains deviations from the light levels desired and needed to perform daily activities. We further translate these into general principles for circadian lighting. We use experimentally validated models of the human circadian pacemaker to introduce a new algorithm to mathematically optimize lighting schedules to achieve circadian alignment to the 24-h cycle, with constrained deviations from the light levels desired for daily activities. Our suggested optimization algorithm was able to translate our findings into general principles for circadian lighting. In particular, our simulation results reveal: (1) how energy constrains drive the shape of optimal lighting profiles by dimming the light levels in the time window that light is less biologically effective; (2) how inter-individual variations in the characteristic internal duration of the day shift the timing of optimal lighting exposure; (3) how user habits and, in particular, late-evening light exposure result in differentiation in late afternoon office lighting.
Highlights
Light is known to influence human physiology and behavior, as it directly stimulates the human biological clock
This work describes an adaptive office lighting system; we assume that light can be tuned only during the office hours
The lighting profile for each employee is presented in Figure 4, representing what we consider as typical light levels in modern societies
Summary
Light is known to influence human physiology and behavior, as it directly stimulates the human biological clock. We exploit one of the most widely adopted models of the biological clock—namely, the Jewett–Forger–Kronauer (JFK) model [15]—to introduce a novel optimization algorithm that finds the best office lighting profile to re-align the body’s natural rhythm to the 24-h cycle This requires us to align the socially induced (by working times) sleep-wake cycle to the natural circadian sleep-wake cycle. One can simultaneously address energy-conservation goals, improve comfort, avoid fatigue, and support task performance If it takes circadian effects into account, Human Centric Lighting may safeguard the health and wellbeing of employees, and it can reduce the long-term health problems associated with circadian disruption, including sleep problems, mood disorders, diabetes, obesity, cardiovascular disease, and cancer [13]. We believe that this explains the experimental findings that generic solutions are less effective than hoped for, and this paves the way to more effective Human Centric Lighting that centers on the individual rather than on a fictitious, population-average person
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