Spotlight on humans
Thanks to new lighting technologies, human centric lighting is now a viable approach to lighting design. David Scott of BAG Electronics explains
The interaction between natural daylight and our ‘inner clock’ has been established for some years, and there have been a number of attempts to mimic these effects using artificial lighting. Such attempts have tended to be costly and limited by the characteristics of traditional lighting technologies. However, the latest LED lighting technologies, have made human-centric lighting (HCL) a practical and affordable reality.
HCL focuses on the influence of light on the natural circadian rhythm, which manages the daily fluctuations of three key hormones — melatonin, cortisol and serotonin. Melatonin is a natural soporific that is produced in the evenings and makes us relaxed. In contrast, cortisol and serotonin makes us more alert and mentally active. The actions of cortisol and serotonin are inhibited by melatonin.
For many years it was believed that there were only two types of receptor in the human eye — rods and cones. However, in 2002 a third receptor was discovered. It contains a pigment called melanopsin, which regulates the biological effects of light with particular sensitivity to blue light (peak sensitivity 480 nm); when stimulated by light, these cells trigger a chain of actions that regulate levels of cortisol, serotonin and melatonin.
In the mornings, powerful, bluish daylight suppresses the production of melatonin, making us more alert. In the evenings, daylight takes on a reddish hue and stimulates production of melatonin which, in turn, suppresses cortisol and serotonin — so we feel tired.
Consequently, the more an artificial illumination system resembles the spectral range and distribution of natural sunlight, the better the quality of the light. HCL seeks to mimic these in a number of ways.
• Matching light output to the natural spectrum.
• Varying spectral composition through the day.
• Using wide, flat luminous surfaces analogous to the sky dome.
• Directing light from the upper visual hemisphere into the eye.
New lighting technologies, in particular LEDs, are at the heart of HCL. Using LEDs it is possible to offer both tuneable white and RGB light from a single source. However it is essential to use high-quality, precisely calibrated LEDs to deliver the required accuracy and stability of colour temperature and a colour-rendering Index with a MacAdam colour tolerance score of <3.
Controllability, clearly also important, comes from the ability to use DALI, DMX, 1 to 10 V and wireless (ZigBee) control protocols, with a number of potential ‘human-machine interfaces’, including both Android and iOS platforms.
Understanding the potential of HCL is most clearly illustrated by considering some of the key applications for this lighting design concept.
Colour-controlled LED lighting can be used to mimic the natural variation in daylight and restore the natural waking/sleep patterns that many hospital patients find difficult to establish. There is considerable evidence that this improves patient outcomes, shortens recovery times, eases depression and facilitates a good night’s sleep.
There is also evidence to suggest that using light with a high blue content in nurses’ stations helps them to remain more alert and reduces the risk of accidents at night.
Similar principles can be applied in the education sector, using light to promote student attentiveness and support deeper concentration for longer periods of time.
Clearly, there is huge potential for HCL in the workplace, because of its ability to improve productivity and the sense of well-being of staff. Studies have shown that work performance can be increased by 19%, with a 31% increase in the alertness. At the same time fatigue is reduced by 27% and light headedness by 34%.
Increased productivity and reduced error rates have also been reported in industrial applications, especially in relation to repetitive work. The spectrum can also be manipulated to increase alertness of night workers, thereby improving productivity and safety.
In a retail environment there are a number of potential uses for HCL, such as creating a pleasant ambience, emphasising different zones and accommodating changes in layout and highlighting particular displays. Of course, it can also be used to ‘extend daytime’ in a shopping mall or large store.
This ‘mood support’ also has uses in the hospitality sector, such as providing a bright and cheery light at breakfast time in a hotel restaurant, changing into a warm and more relaxing environment for the evening. The lighting can also be used to accentuate architectural and design features and to brighten up traditionally dark areas such as corridors and lift foyers.
In terms of applying these principles, there are now packages on the market that provide a complete system, including a converter and human-machine interface, ranging from relatively basic configurations through to premium systems for high-end applications.
For all of these packages, the underlying principle remains the same — namely, putting the spotlight on humans and ensuring the lighting supports their activities, health and well-being.
David Scott is regional manager for the UK and Ireland with BAG Electronics GmbH.