LED Lighting Technology Continues To Advance

Achieving an ideal lighting scenario with LEDs calls for consideration of myriad characteristics.


https://facilityexecutive.com/2015/03/quality-illumination/
Achieving an ideal lighting scenario with LEDs calls for consideration of myriad characteristics.
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Lighting Trends: Quality Illumination

LED Lighting Technology Continues To Advance

Trends-Back-To-FutureBy David Ziolkowski, LEED AP
From the March/April 2015 issue

Great Scott! Yes, 2015 has arrived. Robert Zemeckis may not have offered much in the way of lighting predictions in Back to the Future, but lighting landscape has been rocked since Doc and Marty hit 88 miles per hour in that film some 30 years ago. Lighting products of the 1980s are a reminder that the future is here, but for how long and how do facility decision makers keep pace? If one hopped in the DeLorean and went back just five years ago (or even one), they might be surprised by how fast and how far LED lighting has advanced. LEDs offer the potential of longer life luminaires with better energy efficiency than traditional Y2K sources such as fluorescent, metal halide, high pressure sodium, and halogen incandescent. And LEDs offer a unique form factor and directional source that allows for new and creative applications. But what about lighting quality? Are end-users better off today than they were 30 years ago (or five, or one)?

As an architectural lighting designer, I’m not sure a lighting application exists today where LEDs shouldn’t be considered. If LEDs aren’t selected to move forward, 99 times out of 100 the reason is cost. Energy codes are ubiquitous and continue to force lighting’s connected power downward; hence the need for highly efficient equipment. In the last decade, LED luminaires have displayed great performance when emulating focused and directional Y2K sources. This is why LED has deeply penetrated markets such as roadway, retail accent, and recessed downlighting.

With the appropriate lighting controls, the quality of the lighting environment can be improved dramatically. At TD Ameritrade headquarters in Omaha, NE, approximately 5,000 lighting control sensors are used to harvest daylight.
With the appropriate lighting controls, the quality of the lighting environment can be improved dramatically. At TD Ameritrade headquarters in Omaha, NE, approximately 5,000 lighting control sensors are used to harvest daylight. (Photo: Tom Kessler.)

But it is still difficult for LEDs to compete with linear fluorescent lamps when it comes to performance. Troffers and direct-indirect linear pendants have only recently seen the LED source outperform the original fluorescent versions. Meanwhile, fluorescent lamp manufacturers are touting longer life themselves.

LED manufacturers are still working to create the perfect “global distribution” source. While there have been advancements on the residential light bulb (dimming compatibility is still a sore spot), it is difficult to find a true omnidirectional, linear LED “lamp.” This might just be the Holy Grail. But keeping pace with future maintenance remains challenging. LED luminaires will not last forever. For better or worse, the lighting industry is merging with the electronics industry. In 2025, facility professionals may not want to own the light they buy in 2015. It will be an energy hog as technology marches onward toward the luminous efficacy theoretical limit of 683 lumens per watt. Many LED luminaires sold today are disposable, which can make it complicated and expensive to change out the LEDs in the field. It might be better to purchase a whole new luminaire. It seems logical for the LED industry to focus on easy “fluorescent-like” future changeability but also be upgradeable to the latest energy efficiency technology, much like memory cards (8GB > 16GB > 32GB, etc.).

Efficiency has an enormous impact on lighting quality. In 2013, TD Ameritrade moved into its newly constructed headquarters in Omaha, NE. Having earned LEED Platinum certification in 2014, the 530,000 square foot, 12 story building features LED lighting, further enhanced with controls.

LED has surpassed nearly all of its Y2K competitors in efficiency and life, so manufacturers have turned their attention to that third leg: cost. Value engineering of LED luminaires may produce a smarter housing design here or a more efficient casting there, but will the heat dissipation mechanism become compromised? What variables might stakeholders be considering? Maybe last summer’s LED chips will be “good enough” this spring; after all they were bought on sale, and improved efficiency isn’t quite as important as it once was ever since LED performance surpassed Y2K sources. Perhaps the newest chips are bought, but less of them are used. They are then overdriven to compensate, shortening the luminaire’s life.

Trends-SLIDERSince the color consistency of Y2K sources was so poor, why bother with the expensive LED bins’ 1-step or 2-step MacAdam’s ellipse compliance when three or four or five is “good enough” and the difference is barely noticeable? Color stability over time is critical and is measured in McAdam ellipses (also known as “steps”). Step 1 (the best scenario) is noticeable, but barely. Variation of McAdam ellipses steps 4 and 5 are considered very good, while a step 7 color difference will be very noticeable.

And why bother with a 90 CRI (Color Rendering Index) LED when an 80 or 70 CRI LED is actually perceived to be better than an 85 CRI compact fluorescent per the NIST CQS (National Institute of Science & Technology Color Quality Scale)? After all, LED distribution of light across all wavelengths is superior to fluorescent, which uses carefully selected phosphors to “cheat” its CRI rating. The proper mixing lens and secondary reflector will rid the downlight’s beam of its color inconsistencies, which can often include a bright white center and a dark brown or yellow edge, but perhaps end-users can live without it. Maybe the beam striations are acceptable too without a diffuse lens. If the lens sits a little bit lower and the glare control is shortened, the product performs with increased efficiency and seemingly no downside, right? Actually, there are downsides. An environment’s lighting quality quickly begins to suffer dramatically with these shortcuts.

Lighting controls have become far more simplistic and far more complicated at the same time. Individually addressable dimmable luminaires allow for a simple installation via a low-voltage control loop and unlimited future flexibility via programming. It also requires a sophisticated commissioning process ensuring that daylight sensors, occupancy sensors, scene controllers and the like are functioning the way the design team and building owner envisioned them. White LED light color tunability, between warm white and cool white, is technology that can allow a building’s artificial light to simulate natural light’s color temperature. This can have a significant positive effect on the circadian rhythms of the building’s occupants. A similar but more simplistic version of color tunability is “warm-dim,” where the LED color temperature warms as it dims, turning to an orange-ish red version of white light. When daylight, candles, fire, and incandescent lamps dim, they do so with warm-dim naturally. This is an inherent property of light that human beings are used to dating back centuries. When LEDs dim without warm-dim, they do so at a static color temperature, and it seems unnatural. When someone has full control of their lighting environment, it gives them a sense of comfort, just as they receive from well-designed lighting systems and an excellent quality of light.

Thirty years ago, the type A luminaire on a project may have been an A-lamp incandescent downlight. It was well shielded to provide a 50° cutoff angle for occupant comfort, dimming with no flicker and dimmed to warm. It had a perfect color rendering index of 100. Its reflector and cone were engineered to provide a smooth beam gradation with no striations. Since then, the compact fluorescent downlight had its day, with all its glare, poor luminaire efficiency, expensive dimming ballasts, and uninspiring lighting environments. Today, a well-designed LED downlight can achieve everything the A-lamp could at perhaps a tenth of the energy. Only it can’t if a poorly designed LED downlight is selected. So is lighting quality better off today than it was 30 years ago (or five, or one)? The past is the past. Or maybe the past is the future. It all depends on the path chosen.  

Ziolkowski.
Ziolkowski

Ziolkowski is a senior associate and senior project lighting designer with HOK in St. Louis, MO. He is a professional member of the International Association of Lighting Designers, a member grade professional of the Illuminating Engineering Society, and lighting certified by the National Council on Qualifications for the Lighting Professional. He has been with HOK for 14 years.

 

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