I recently had the pleasure of interviewing Scott Roos, VP of Product Design, Juno Lighting Group, on the topic of tunable-white lighting. I’m happy to share his responses with you here. The interview informed an article I wrote for the May 2016 issue of tED.
DiLouie: Looking at LED sources and controls, what are the different technological methods used to produce tunable-white light in commercial luminaires?
Roos: RGB color mixing is a long-standing method, but this model has poor color rendering and many technical and performance limitations, so it is seldom used outside of creating theatrical, colored lighting effects. There are multi-channel drivers that allow varying the intensity of two to three different color temperature, phosphor-converted white LEDs. And then there are hybrid multi-channel systems that combine nominally white phosphor-converted LEDs with one or more monochromatic colors to achieve a higher quality and greater range of tunable white lighting effects.
There are many control protocols that can be used with tunable white lighting, but each system is designed to be compatible with a specific one. At one extreme, there exists the conventional, economical and easy-to-commission phase and 0-10V dimming. At the other extreme, DMX and DALI systems provide more capabilities but are more costly and require a greater degree of commissioning. And then there is the emerging field of using smart devices to wirelessly commission and control fixtures using protocols that include Bluetooth and Wi-Fi.
DiLouie: What are the different effects that can be created, such as color stability/consistency, dim-to-warm, CCT selection?
Roos: Warm-to-dim is the easiest effect to employ and understand. What’s required is simply connecting the luminaire to a compatible dimmer and it behaves like an incandescent or halogen lamp to create warmth and intimacy in settings such as homes, restaurants, hotel rooms, bars, etc. where this shift in ambiance is expected and appreciated.
CCT selection allows the color temperature to be changed post-installation independent of dimming. This can be a static selection to set the CCT to exactly complement a given interior décor, or it can be dynamic where scenes are set or automatic color temperature changes are programmed into a lighting control system. Dynamic tunable white systems enable users to change the appearance of the space from warm to cool depending on time of day or activity.
More sophisticated multi-channel hybrid LED systems with phosphor-converted white plus color settings allow spectral tuning of the luminaire beyond CCT. The multiple color channels can fill in missing or deficient spectrum of the phosphor-converted white LED to create exceptionally high color rendering and color fidelity. The color point can be moved off the Planckian locus – the reference for what humans perceive to be natural white light – to enhance interior finishes, art and store merchandise. Additionally, the spectrum can be optimally tuned to support circadian health and productivity. And these more sophisticated systems typically employ thermal and optical sensing and feedback systems to help tightly manage out-of-box color consistency and color stability over the service life of the luminaire.
DiLouie: What markets and applications do different tunable-white lighting effects serve? What’s the low-hanging fruit?
Roos: Applications for warm-to-dim in residential and hospitality settings are the low-hanging fruit, as they are essentially replicating the expected and appreciated effects of long-standing incandescent and halogen technology. The technology can be relatively inexpensive and requires no additional design or commissioning time or expense, so there are really no barriers to widespread adoption.
Tunable white lighting, on the other hand, is opening up an entirely new frontier in lighting design and human health and productivity. For aesthetic-driven applications, there are many low-hanging fruit opportunities – with the limiting factors being education, willingness for an end user to pay for the incremental cost of the luminaires, controls and commissioning. High-end retail, hospitality, art and museum lighting stand out as examples of early adopter applications that can realize the most compelling benefits from this technology.
Tunable white lighting for human health and productivity is on the cusp of pioneering applications coming online in healthcare, education, performance sports and 24/7 work environments. As with any new frontier, a few end users have jumped right in to install beta sites or small scale applications because the benefits of improved quality of life and/or increased performance hold so much promise. Others are taking a ‘wait and see’ attitude, sitting on the sidelines until well documented case studies that quantitatively substantiate claims and IES recommended practices are published; at such time, they will have the confidence to move forward and avoid potential liability.
DiLouie: How would you characterize demand for tunable-white lighting?
Roos: It is in the very early adopter stage with tremendous opportunity for growth. Even the most basic warm-to-dim technology is at the early stages of what is sure to be exponentially growing demand.
DiLouie: Color temperature has been linked to circadian lighting. What is the link, what research supports it, and how should distributors be selling it?
Roos: It is not actually color temperature, per se, but the spectral content of the light that is linked to our circadian response. Exposure to short wave blue light centering on 480 nanometers has been shown to suppress melatonin and stimulate the production of neurochemicals that promote alertness and health during the day and cause sleep disruption and negative health effects at night. While there is a correlation between color temperature and spectral content, it is important to understand that traditional lighting metrics developed around the human visual response system such as CCT, lumens and footcandles are not accurate predictors of a circadian response. New metrics, such as melanopic lux, are being developed and proposed to support the design and application of circadian lighting.
In regards to selling circadian lighting, distributors should stick to educating customers on the basic facts without making specific health claims and take extra care to do no harm. For example, warm-to-dim LEDs used at home will certainly support better circadian health than static white LEDs, and a cooler 5000K or 6500K CCT luminaire for 100 percent daytime application will likely promote improved alertness, productivity and mood. When looking at applying more sophisticated spectrally tuned luminaires and controls to optimize the lighting for a hospital, extended care facility, school or 24/7 work environment, for example, distributors and end-users need to work with a professional who has done their homework and has access to the research and researchers that can be found in organizations such as the Human Centric Lighting Committee or the Light and Health Alliance at the Lighting Research Institute. Informed members of these groups can help guide their efforts to ensure the desired results and provide safeguards such that the spectrally tunable lighting system cannot be misapplied and cause harm.
DiLouie: If you could tell the entire electrical industry just one thing about LED tunable-white lighting, what would it be?
Roos: While I can’t predict how quickly tunable white technology will see wider adoption, I can confidently state it is only a matter of time until it does. This is a unique opportunity for industry professionals to invest in education on this topic to position themselves as the experts who will be the ones to advance this emerging field in lighting. It holds great promise to improve the quality of our interior environments and positively impact human health, well-being and productivity.