Expanded Reach: Tuning Up LED Performance

A decade ago, lighting products using LEDs were just breaking into the broad commercial market for limited applications and, at times, considerable expense. Today, LED fixtures and lamps meet or exceed performance targets set by legacy incandescent, fluorescent and halogen technologies, and product developers are expanding into new light quality and control capabilities unique to LEDs. In addition to providing new design possibilities, the latest offerings could help improve users’ health and productivity.


The growing maturity of LED products can be seen in just about any market-research firm’s sales forecasts. In March, Strategies Unlimited forecast annual LED lamps sales would grow to 4.5 billion units by 2022, from 2015’s 1.7 billion figure. The firm projected luminaire sales to hit $45 billion by 2022, more than double 2015’s $20 billion total. The selling points of efficiency, longevity and performance obviously are hitting home.


“Now, LEDs are just the default lighting solution, unless you have facility managers who just prefer [an older technology],” said Ed Clark, sustainable designer with Portland, Ore.-based ZGF Architects.


Additionally, Clark is seeing new luminaires that are taking advantage of LEDs’ slim form factor and unique lighting characteristics.


“Finally, I think the manufacturers are getting out of the paradigm that everything has to look the same as they used to,” he said.


At the advanced end of new-product development, manufacturers also are looking at how the controllability of LEDs could add new functionality to lamps and luminaires. Internet-connected lamps that can change colors with the use of a smartphone app, such as Philips’ Hue products, are one example of such capabilities.


More significant, though, are new commercial fixtures that offer some of the following features:


Warm-to-dim color shifting mimics the way incandescent lighting dims to a warmer color. Restaurants and other hospitality venues use this feature to change the mood of a room over the course of a day.


Tunable white capabilities enable users to adjust the color of a fixture’s light output across a broad range of correlated color temperatures (CCTs). This capability is being explored for the ways it can boost our natural sleep and wake cycles as well as potentially improve productivity.


Dynamic RGB (red/green/blue) color adjustment enables scene setting and scheduling at a sophisticated level using easily addressable controls. Designers are exploring this option in retail settings, theaters, theme parks and other such “architainment” applications.


Philips' Hue smart home light is controlled by a smartphone app.
Philips' Hue smart home light is controlled by a smartphone app.

 

Color complications


There is a learning curve to using these new features, which could begin with a conversation on the meaning of the word “color.” Unless one is talking about RGB-related features, when it comes to lighting, color is generally a reference to “white” light—the light we see when we flip a wall switch or turn on a table lamp. In this context, color is measured by a light source’s CCT, measured in kelvins (K). Warmer, yellow- or orange tones are at the low end of this scale and cooler, bluer tones are at the higher end. Candlelight, for example, falls at about 1,800 K, while daylight can be measured at 6,500 K or higher.


In making the transition to today’s LEDs, a lamp or fixture’s CCT is often seized on as a way to understand what a new installation’s illumination will look like. However, because LED manufacturers can use different technical approaches to reaching the same color temperature, trusting CCT alone to anticipate light output appearance in a specific setting can lead to disappointment.


“Especially with LEDs, you can have the same CCT, but they can render differently,” Clark said. “I think you need to understand color in a much more robust way.”


Clark’s firm once replaced adjacent fixtures several months apart. Though the products’ listed CCTs were identical, the actual color of the light output differed because the manufacturer had changed the internal chipset in the time between the two purchases.


How is it possible that illumination from sources measured to have the same color temperature could look different to the human eye? Part of the answer with LEDs lies in the way manufacturers choose to create light with a specific appearance. For example, light our eyes perceive as yellow can be produced simply by using chips set to produce light at that specific wavelength or by mixing the output of chips producing light in red and green wavelengths, said Mariana G. Figueiro, director of the Lighting Research Center (LRC) at Rensselaer Polytechnic Institute in Troy, N.Y.


To address this, designers and contractors should pay more attention to spectral power distribution (SPD) in their specification efforts. This metric is generally represented as a graphed curve that illustrates which wavelengths along the visible light spectrum predominate in any light source. Light sources can reach the same CCT with very different SPD profiles. So, while their light output might look the same, their effect on the appearance of the color of furnishings and wall colors can be very different.


“We at LRC say that color is actually a figment of your imagination,” Figueiro said. “Color is very misunderstood, and the way we specify color is very different than how we see color. I think people mix up the physical measurement with perception.”


 

Aiding body rhythms


CCT remains effective as a means of describing the warmth or coolness of a light source’s output, and that knowledge is becoming more important as we learn more about how light affects human health—specifically, how it relates to our circadian sleeping and waking rhythm. Natural daylight stimulates wakefulness as it triggers a process to reduce production of melatonin, a hormone that supports sleep. In the human body, melatonin production increases as the sun sets.


Since the 1980s, lighting researchers have understood that electric lighting has the potential to support human circadian rhythms. Now, LED manufacturers are introducing “tunable white” products that cycle through a range of color temperatures and intensities in an effort to bring circadian-enhancing benefits to schools, healthcare facilities and offices.


Many of these products operate between a CCT range of 2,700 K and either 4,500 K or 6,500 K. Figueiro said the exact color temperature at each extreme in these light sources is less important to our circadian cycles—and our psychological responses toward wakefulness and sleepiness—than the range between those extremes.


“The circadian response has a peak at 460 nanometers,” she said, describing illumination at the upper, bluer end of the visible light spectrum. “As you move away from that peak, or when you have white light and start spreading the energy across the spectrum, you reduce the effectiveness.”


The first markets for tunable white products have been healthcare and education. While lighting experts are still working out best practices for a true circadian response, hospitals and nursing facilities see the technology as a way to reinforce sleep patterns in potentially disorienting environments. 


Schools hope to aid student focus and productivity.


“When the kids come into the classroom in the morning, the teacher may want to increase the CCT to 4,500 K or higher because the bluer light facilitates awareness,” said Jamal Smith, manager for commercial downlighting in the architectural indoor category for Hubbell Lighting.


After recess, a teacher might want to lower the CCT to calm some of that youthful energy. Hubbell Lighting recently introduced its SpectraSync technology to bring tunable white capabilities to a number of its existing downlight lines.


Coloring the world


When it comes to warm-to-dim and RGB color-changing capabilities in commercial settings, the focus is mostly on using light as a scene setter. Bonnie Littman, president and CEO of USAI Lighting, said hospitality and retail have been very interested in how color-tunable fixtures can help spaces adapt to multiple purposes.


“Hotels and retailers are definitely early adopters of color-tuning technologies,” she said. “But, we are also seeing how these products are being applied in corporate settings for branding and productivity. Tunable color LED products offer a variety of industries the flexibility to tailor their lighting solution to fit their needs and the atmosphere of their space, all within a single lighting fixture.”


One important criterion for success with all the adjustable lighting technologies is to maintain simplicity in their controls, even as functionality continues to increase. Even a capability as seemingly simple as dim-to-warm requires attention to multiple variables. The color shift to warmer temperatures was a natural byproduct of reducing the power with incandescent lamps. LEDs don’t perform that way, so fixture and lamp designers today have to figure out how to reduce color temperature in sequence with reducing light output.


Hubbell, for example, incorporates two sets of LEDs at high and low CCTs that shift intensity as output is decreased or increased, according to Smith.


“We have a control module that we’ve designed so it’s very easy for the end-user,” he said. “We just made everything happen behind the scenes. You want to keep things simple and mimic solutions people already have access to in the field.”


A continuing emphasis on the user experience will be critical to the success of dynamic lighting, Clark said. He is an advocate of giving occupants control over dynamic lighting levels, even in settings where white and RGB color-changing schedules are hard-programmed into building operations. He is hopeful that identifying more connections between health and lighting, along with falling costs, will make dynamic lighting a standard offering over the next decade.


“I would hope that, within 10 years, this will be seen as an archaic conversation,” he said.


About the Author

Chuck Ross

Freelance Writer

Chuck Ross is a freelance writer and editor who has covered building and energy technologies for a range of industry publications and websites for more than 25 years. He specializes in building and energy technologies, along with electric-utility...

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