Bringing the sunshine into the office with human centric lighting

Today people spend most of their time indoors with artificial lighting – even more so over the past two years due to coronavirus. Pre-pandemic, biologically effective lighting was a hot topic in the lighting industry, with research suggesting it is really beneficial to adapt it to the circadian rhythm of the user, particularly in an office environment, writes Paul Jones, Sales Director UK & Ireland, B.E.G.

With more people returning to the office, organisations are again looking at ways to make these spaces as safe, healthy and inviting as possible. The aim of it is to support natural active times and rest phases during the course of the day in a meaningful way.

Artificial lighting has long been used to be active at any time of day or night. That this is not always healthy, as has long been shown by studies with people who work in shifts, for example. In recent years, however, new findings were made that prove that natural light plays a much greater role in human wellbeing than previously assumed, with the light colour being very important.

Scientists found out that the colour of light controls the human hormone balance and thus sets the human internal clock. Therefore, lighting control now makes use of these findings: Human Centric Lighting places people and their natural biorhythms at the focus of modern lighting control.

The effectiveness of light colour on the human biorhythm was only discovered in 2002. Scientists found a third, previously unknown light receptor in the human eye in addition to the already known light receptors (cones and rods for colour and twilight vision).

The so-called ganglion cells are sensitive to light and control biological processes in the body such as the pupil reflex or hormone production. One to three percent of the ganglion cells respond to the colour of light, or more precisely to the blue component in light. If the blue component is low, the production of the sleep hormone melatonin is triggered – if the blue component is high, the production of the stress hormone cortisol is triggered.

The light has a great influence on whether we feel tired or awake. In natural light the blue component varies throughout the day, thus supporting the human biorhythm. B.E.G. has been manufacturing lighting control products for more than 40 years and, in order to bring this effect to indoor areas, the company has developed the PureColour occupancy detector. By controlling the colour of light, it brings the dynamics of daylight back to people. The occupancy detector can gently and unobtrusively support both the performance and the wellbeing of the room users.

Few components are required for HCL light control in an office. The sensor includes an integrated tuneable white function. No additional controller is needed to control the light colour – the occupancy detectors can be connected directly to the luminaires.

The panel luminaires in the modular ceiling of the office must, of course, be designed for colour change. The LED panel luminaires are equipped with warm white and cool white LEDs that can be controlled separately. The LED driver operates according to the DALI Device Type 8 Standard for Tunable White. This not only allows the luminaire to be dimmed, but also allows the colour temperature to be freely adjusted from warm white (2,700K) to cool white (6,800K).

With installation and commissioning, the lighting in the office is completely tailored to the needs of the room users. Like other DALI occupancy detectors, HCL sensors control different luminaire groups based on presence and daylight, covering an area of up to 24m. Up to 64 DALI electronic ballasts can be controlled via the detector.

The sensor contains the luminaires for the main light which can be divided into three groups and be given offset values. This compensates for brightness differences in the room, for example, if the room has windows on one side only. The percentage gradation of the brightness of the luminaire groups from the wall to the window ensures that the darker wall area is more strongly illuminated than the brighter area at the window. This means that the room is uniformly lit everywhere.

There is a separate zone for DALI group which is intended for accent lighting, for example, for blackboard lighting in classrooms. A third zone is controlled by a switching relay integrated in the detector that can be used, for example, to connect the air conditioning system. In this way, the ventilation can also be controlled depending on the presence of people.

After grouping the luminaires, the HCL lighting control system can be put into operation. The pre-programmed factory settings cover the most common requirements but can be overwritten individually. All connected luminaires are controlled energy-efficiently by the occupancy detector. The measured brightness value is used to add only as much artificial light to the natural light entering through the window as is actually needed to meet the required brightness in the room.

In essence, HLC sensors automatically control the light colour and brightness in the room over the course of the day. According to the use of the room, pre-set application profiles can be selected. They operate completely independently thanks to its real-time clock and integrated DALI controller. This allows each room to be configured individually. The change in light colour from warm to cool white and the change in brightness are based on the biological rhythm of human beings. This happens very slowly and imperceptibly for the users, just like with natural light. That is how the biological light effect of the sun is brought into the office.

The light has a great influence on whether we feel tired or awake

B.E.G., luxomat.com

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