Workshop Presentations and Materials 

Lighting leaders from all across the country gathered in Portland, Oregon, November 8, 2017, for DOE’s 12th annual Solid-State Lighting Technology R&D Workshop, which was followed on November 9 by the Next Generation Lighting Industry Alliance (NGLIA) SSL Technology Trends Workshop. The diverse audience spanned the spectrum of SSL stakeholders, representing lighting, control, and components companies as well as research institutes, academia, national laboratories, municipalities, designers, specifiers, and distributors. The workshops’ purpose was to create a forum for airing application and performance issues related to the current level of solid-state lighting technology development, and to explore emerging capabilities being enabled by ongoing advances in SSL and controls technology.

PRE-CONFERENCE GUIDED TOUR OF DOE’S CONNECTED LIGHTING TEST BED

On the evening of November 7, a pre-workshop tour of the DOE Connected Lighting Test Bed (CLTB) provided attendees with a close-up view of test bed setups designed to examine the energy reporting capabilities of Power over Ethernet and other connected lighting systems, and how application programming interfaces (APIs) are facilitating interoperability. One demonstration illustrated the variation in response time to a lighting-change request sent via API to six different connected lighting systems, and highlighted the fact that these first studies are not only generating valuable data to inform the efforts of standards committees, task groups, and consortia, but are also identifying issues that require further investigation.

WELCOME

DOE SSL Program Manager James Brodrick provided an introduction to the workshop sessions, inviting attendees to learn, share, and participate. He observed that although today’s highest-performing LED devices have efficacies of 160–170 lm/W, DOE projects that 250–350 lm/W can be achieved. Brodrick said LED lighting opens the door to new opportunities and applications that go way beyond simply lighting a space, noting that we’re just beginning to understand how to manipulate the light spectrum to best grow indoor crops, improve the patient environment, and use streetlights to monitor traffic flow and air quality and detect crime. “These new opportunities for lighting challenge the old thinking, and raise important new questions,” he said, adding that DOE research looks to augment our understanding of this paradigm-shifting technology.

HOW FAR CAN WE GO?

The workshop’s keynote address was given by Kevin Dowling of Kaarta, who reminded the audience that today’s lighting revolution is just getting started and, after a quick look back at SSL’s history and progress to date, presented a vision of what else can be done with new generations of digital lighting. In considering what’s next for SSL, he focused on improved performance, lower cost, better quality, new form factors, new connectivity, wider usage, and better consumer education. Dowling noted that when incandescent technology prevailed, lighting accounted for 15% of a typical residential electrical bill, whereas with LEDs it only accounts for 2-4%, which lowers the incentive for consumers if they’re considering energy savings alone. He said that while performance will continue to improve, there won’t be the massive savings we saw in the past 10 years, but that with new form factors, controls, and integration into networks “there’s a huge opportunity.”

HORTICULTURAL LIGHTING SCIENCE AND SSL TECHNOLOGY

Nick Klase of Fluence spoke about horticultural lighting. To convey its importance, he cited the massive and growing world population, noting that the United Nations predicts that by the year 2050 we’ll need to grow twice as much food as we grow today – but that there’s not enough area to do that, so 70% of that additional growth will have to come from efficiency improvements in the agriculture industry. Klase observed that horticultural lighting has a huge impact on the electric grid, with indoor horticulture alone consuming 1% of the nation’s electricity. He explained that whereas most horticultural lighting today is high-pressure sodium (HPS), LED not only has more potential for energy savings, but also offers greater tunability, which is important for increasing crop yields. Using a football analogy, Klase said right now we’re only on the one-yard line when it comes to getting the most out of SSL – which means there’s practically the entire length of the field to cross before we can, so to speak, score a touchdown.

BUILDING THE EVIDENCE ON HOW LIGHT AFFECTS HUMAN HEALTH

Bob Davis of Pacific Northwest National Laboratory (PNNL) moderated a panel that focused on the growing body of scientific evidence of the ways in which light affects human health, and that included principal investigators for two new DOE-funded research projects. Noting that two Nobel prizes that have been awarded in the past four years have been for lighting-related work, Davis made the point that there’s still much we don’t know about the effects of lighting on human health, which he said is an issue that’s taken on increased relevance because of an aging population and the prevalence of sleep-related disorders, which affect 70 million people in this country. He noted that the discovery, about 15 years ago, of the human eye’s intrinsically photosensitive retinal ganglion cells (ipRGCs), which affect the body’s production of the hormone melatonin, has stimulated much research into light’s effects on circadian rhythm. Davis briefly reviewed several GATEWAY studies on the topic, explaining that one gap they’re intended to address is how to start documenting these physiological responses in real-world settings.

Ron Gibbons of the Virginia Tech Transportation Institute (VTTI) described three state-of-the-art DOE-funded experiments he and his team are conducting to increase our knowledge in that area by investigating the health impacts of outdoor lighting on drivers, pedestrians, and sleepers under carefully controlled conditions. He noted that although there are about 90 scientific papers on the topic, many of those laboratory studies are based on unrealistically high dosage levels, calling the results into question. Gibbons said the experiments will be conducted in VTTI’s “Smart Road” facility and will measure the impact of different lighting types on melatonin in the blood of users of a lighted space at dosage levels appropriate to that space. He explained that CCT “is an appearance metric and not a performance metric” and thus is a misguided metric for use in studies on the physiological effects of light.

Neuroscientist Gena Glickman of the University of California at San Diego discussed how she and her team are helping to answer similar questions about the effects of indoor lighting by studying novel lighting strategies for optimizing circadian and sleep health in nightshift workers. She, too, emphasized the importance of realistic parameters, cautioning that a controlled lab environment doesn’t necessarily translate to real life. Glickman noted that 15 million Americans work outside of a nine-to-five schedule, and that this can cause accidents and injuries as well as health consequences. She explained that the harm is due to three factors – circadian misalignment, sleep deprivation, and light at night – and that lighting can be used to facilitate circadian adjustment or increase alertness and performance, or it can be minimized to reduce any disruptive effects. Her study, Glickman said, will involve all three strategies and will focus on the timing, intensity, and wavelength of the light.

HUMAN PERCEPTIONS OF COLOR RENDITION

PNNL’s Michael Royer talked about human perceptions of color rendition, highlighting key findings from several studies conducted since the publication of IES-TM-30-15, which is a method for evaluating light-source color rendition. He said that TM-30 improves upon methods such as CRI because it’s more accurate and more comprehensive. Royer emphasized the importance of accurately characterizing color rendition in enabling manufacturers and specifiers to deliver the best possible lighting solutions. He noted that humans have a built-in affinity for reds, but that CRI penalizes red saturation and thus militates against developing light sources that people like. Royer stated that average color fidelity alone is unrelated to any perceptual attribute, and that developing narrowband emitters and phosphors is really important for developing high-quality, high-efficiency products.

LED STREET LIGHTING, BLUE LIGHT, AND SKY GLOW

PNNL’s Bruce Kinzey presented a snapshot of the results from the DOE sky glow study, discussed recent related developments, and previewed a new sky glow calculation tool in development. He noted that recommendations released by the American Medical Association in 2016 kicked off a host of issues pertaining to LED lighting that were complicated by selective assumptions and frequent mischaracterizations. Kinzey explained that broader spectral content does augment street lighting’s impact on sky glow compared to typical incumbent HPS cobra-head type luminaires, but is attenuated by LEDs’ ability to provide equivalent illumination with reduced total light output and to eliminate uplight. He said the sky glow calculation tool being developed by DOE is spreadsheet-based and is intended to enable first-order analysis, such as basic A-B comparisons of sky-glow impacts among products being considered.

ILLUMINATING ENGINEERING SOCIETY UPDATE

Mark Lien of the Illuminating Engineering Society (IES) gave a brief update on his organization. He said IES has a renewed emphasis on standards development and research, and noted that there have been 10 new recommended practices in the past year, in addition to technical memorandums and design guides. Lien mentioned an upcoming IES research symposium that will focus on light and health, and called attention to an informative IES webinar series. He said every recommended practice that comes out from now on will have educational content and will include something that explains the nature of the recommended practice and how it differs from the preceding document, if there was one. Lien called on the audience to let him know of any gaps in the industry that aren’t being addressed.

TECHNOLOGY TRADEOFFS

Morgan Pattison of SSLS Inc. moderated a panel discussion of the tradeoffs between LED package and device optimization and preexisting expectations for lighting cost, performance, form factors, etc., and what can be achieved in fully optimized LED lighting products. Steve Paolini of Telelumen focused on the spectrum. He said the ability to control the spectrum and the source size digitally and efficiently is at the top of the LED value pyramid, and noted that spectral power distribution (SPD) is the definitive description of the chromaticity of a light source and, through reflection, the rendering of an object. Paolini explained that a more continuous spectrum and wider range of wavelengths produce light sources with higher color quality, whereas a less continuous spectrum and truncated range of wavelengths are often more efficient. He also pointed out that spectrum is important for fidelity and preference, that broader wavelength range and less dropout in the SPD increases color quality and impact, and that natural light sources have a broad variable spectrum. Paolini advised specifiers to get a copy of the SPD for all light sources.

Paul Fini of Cree talked about the opportunities and challenges of narrowband spectra and optics. He said narrowband red emission is valuable for high color quality at high efficacy, but may introduce system-level tradeoffs. New spectra, Fini stated, will depend on the development of new efficient and reliable narrowband (<40nm) emitters and downconverters from cyan through red. Narrow emitters, he noted, enable a wider color-tuning gamut, with high spectral efficiency on or near the blackbody locus, but color tuning requires investment in multi-driver control, which is currently taking place, and fixture-to-fixture color consistency requires careful color-point and intensity binning. So far, Fini said, spectra have been optimized for CRI R_a and R₉, but measures beyond those should be assessed when specifying new spectra. He observed that SSL luminaire optics designs are evolving rapidly, and said lightguides should effectively couple LED emission, convey light with little or no loss, and efficiently extract light.

Wouter Soer of Lumileds discussed high-luminance LEDs. He pointed out that high luminance enables better optical control, and explained that there are two ways to increase LED luminance: drive it harder, or reduce the package size/improve collimation. Soer briefly went over the droop phenomenon, which is a decrease in LED efficacy with increasing drive current, and said there are two key factors affecting package efficiency: Fresnel reflection at the exit surface, and reflectivity of the package enclosed by the exit surface. Soer reviewed the diversification in LED architectures, including chip-scale packages, vertical thin-film, thin-film flip-chip, and patterned sapphire substrate flip-chip. He noted that high-luminance LEDs are designed to be driven hard with a small surface area, and that they address the needs of directional applications by enabling smaller luminaire form factors and higher levels of beam control, and by enabling efficacy benefits at the luminaire level that outweigh the efficacy penalty at the LED level. Optical performance, Soer said, is critical.

WHY KEEP PUSHING ON EFFICACY?

PNNL’s Kelly Gordon moderated a panel that considered the factors that stand in the way of fulfilling SSL’s efficacy potential, as well as what we’ll miss if we settle for “just good enough.” She noted that LED products are available for almost all general-illumination applications now, and that the difference between LED lighting and other kinds of lighting is that with LEDs, there’s “this continuing, significant headroom for improvement. They still can improve efficacy a lot over where they are today.”

Charlie Grist of Northwest Power & Conservation Council recounted that last year, lighting accounted for half of all electricity savings in his region. He explained that resource planners need to have just the right amount of resources, which include energy, capacity, flexibility, and other ancillary services needed for system reliability; and that resource cost and risk profile are the big drivers. Grist noted that unlike many other sectors, lighting is on primarily during periods of peak demand for electricity, so improvements in lighting efficiency can play a significant role in demand reduction – and such improvements are far less expensive than building new electricity-generating capacity. Thus, in reducing grid load at peak times, SSL makes the grid more reliable and less expensive to operate – increasing the technology’s value well beyond the cost savings achieved by its users.

Jeff Quinlan of Acuity Brands Lighting considered the various benefits of increasing LED lighting’s efficacy. One benefit, he said, is that we “spend the lumens” needed to do a better job of creating a continuous spectrum, which in turn could enable a range of biological light-related effects in people, plants, and animals. In addition, Quinlan stated, increasing the efficacy means the product produces less heat, which in turn increases its lifetime. He noted that efficacy improvements also allow for much smaller and thinner products, which not only opens up whole new aesthetic possibilities, but also could even affect such things as the height of buildings by enabling the spaces between floors to be smaller. Quinlan said in many areas, electricity is so cheap that energy savings alone aren’t sufficient motivation for some people, so other benefits will be the deciding factors. “We’ve got a huge opportunity,” he said.

Brennan Schumacher of Mazzetti+GBA offered a lighting designer’s perspective, focusing on the perception of light and illustrating his points with real-life design projects. He noted that light is a form of energy that’s all around us, and that we don’t see it unless it’s reflected off of a surface. The two main metrics emphasized by industry, Schumacher observed, are light levels and energy codes. “What we try to do,” he said, “is focus on brightness-based design. We try to reflect light off of surfaces.” Schumacher talked some about the effects of light on human health, and noted that in his design process he starts with daylight, which is the most efficient source of light and creates a healthier environment. The most challenging piece of the puzzle, he said, is how to align with future technology.

NGLIA UPDATE

Jeff Quinlan spoke briefly about the Next Generation Lighting Industry Alliance (NGLIA), which he chairs. He explained that it’s an alliance of lighting manufacturers who’ve made a commitment to support the DOE SSL program in a variety of ways, offering their expertise and input in working groups, studies, and the development of test methods and metrics. The day ended with a networking reception sponsored by NGLIA.

THE SSL TECHNOLOGY TRENDS WORKSHOP

Day 2 was the SSL Technology Trends Workshop, hosted by NGLIA, which shared lessons learned from indoor and outdoor connected lighting installations, results from DOE connected lighting test bed studies, and perspectives on lighting trends that might influence future SSL technology advances. NGLIA chair Jeff Quinlan kicked things off by welcoming the audience and introducing the speakers.

SMART STREET LIGHTING SOLUTIONS FOR THE WINDY CITY

Danielle DuMerer of the City of Chicago reported on Chicago’s smart street lighting project, which is poised to become one of the largest municipal lighting modernization programs in the country, featuring conversion of the city’s current HPS streetlights to a fully connected LED streetlight system. She said the new system, which will include more than 270,000 smart LED lights (85% of the city’s streetlights) and be installed over the course of the next four years, will feature soft white light (3000K or less) that significantly improves vehicle and pedestrian visibility; remotely adjustable light levels; and better-directed, fully shielded lighting that’s put only where it’s needed. DuMerer said it will reduce electricity usage by 60% and pay for itself in nine years, resulting in more than $10 million in annual utility cost savings. She explained that a wireless network and software enable remote monitoring and control, and that the system automatically creates outage tickets, reducing reliance on resident reporting, and shares energy data with the local utility to support billing and leverage information for further analytics.

CONNECTED LIGHTING LESSONS FROM A LIVING LAB

Ruth Taylor of PNNL; Craig Bernecker of Parsons School of Design, The New School; and Chris Wolgamott of the Northwest Energy Efficiency Alliance offered a vivid look at lessons learned so far from a “living lab” set up at Parsons for the Next Generation Lighting Systems competition. They explained that seven different connected lighting systems were installed in classrooms there and are being evaluated for performance and ease of installation from the perspectives of specifiers, contractors, and end users. While the seven systems were marketed as “easy to install and configure,” the experiences of the electrical contractors and NGLS evaluators – who were all seasoned lighting pros – paint a very different picture and offer valuable feedback for manufacturers and specifiers.

WHAT WE CAN LEARN FROM A CONNECTED LIGHTING TEST BED

PNNL’s Michael Poplawski presented a snapshot of various studies underway in the DOE CLTB that focus on such things as the energy-reporting capabilities of Power over Ethernet and other connected lighting systems, how application programming interfaces (APIs) are facilitating interoperability, and the development of test methods for cybersecurity vulnerabilities. He defined a connected lighting device as being controlled, intelligent, connected, and both a data consumer and producer, and he reviewed DOE’s main areas of focus for connected lighting: energy reporting, interoperability, key new features, cybersecurity, configuration complexity, and stakeholder collaboration. Poplawski explained that he and his colleagues at the CLTB are initially developing test setups, which they then implement with specific equipment and develop the test method. He invited the audience to provide feedback. “We’re trying to figure out the most impactful things that we can do, and we would love your assistance with that,” he said.

LIGHTING MARKET TRENDS

Drawing on the latest DOE market studies – U.S. Lighting Market Characterization, Adoption of Light-Emitting Diodes in Common Lighting Applications, and Energy Savings Forecast of Solid-State Lighting in General Illumination Applications – Clay Elliott of Navigant presented an overview of major trends and changes in LED adoption, and examined what it will take to realize the full energy-saving potential of LED technology. He noted that between 2010 and 2015, LED penetration increased from 0% to 7% in the residential sector, from 1.8% to 10.5% in the commercial sector, from 0.4% to 4% in the industrial sector, and from 9% to 23% in the outdoor sector. Elliott added that in 2016, 12.3% of all indoor lighting installations and nearly 30% of all outdoor lighting was LED. He emphasized that while the adoption of LED lighting products is growing, it’s still in its early days, “and substantial headroom remains to increase market penetration and related energy savings.” The largest energy-savings opportunity, Elliott said, lies with LEDs in linear fixture applications coupled with connected controls.

LIGHTING AS A SERVICE

Virginia Hewitt of Sparkfund discussed the concept of lighting as a service (LaaS) and why it’s so compelling for SSL. She pointed out that for providers, LaaS leverages volume to pay back investment in high upfront costs; and for customers, it’s a strategy to access value without the risk and hassles of ownership. If it’s done right, Hewitt said, it allows customers to treat their projects as operating expenses, and since they don’t own the equipment, they’re not locking themselves into ownership and can access better-functioning equipment at tighter iterations. “The service providers and their partners remove complexity from customers, so you don’t need to worry about what products are being spec’d or lumens per watt – you can (just) worry about educating children or building widgets,” she said. Hewitt noted that utilities pioneered the as-a-service model, and that manufacturers are seeing it as a market differentiator. “Everything is included: maintenance, upkeep, continual commissioning – any level of service a service provider wants to bundle in there can fit,” she said.

WILL LED LIGHTING SYSTEMS CHANGE DAYLIGHTING DESIGN?

Andrea Wilkerson of PNNL moderated a panel that considered how the efficiency of LED lighting systems may affect the incorporation of daylight into energy-efficient buildings. She explained that the panel is “not setting out to prove that we no longer need windows because LEDs are all we need,” but rather is intended to discuss the contributions of daylighting in the built environment and how this relates to energy-efficient building design and the increasing use of LED lighting systems.

Craig Casey of Lutron focused on daylight efficacy and energy codes. He explained that three things vary the efficacy of direct solar: air mass, aerosol scattering, and water vapor. Casey discussed the efficacy of diffuse sky and of global illumination, considered what they mean to a building, and examined the efficacy of vertical illumination and the effect of glazing. He noted that no matter how efficacious daylight is, it adds energy to the space, so building owners and occupants should consider the use of automated shading to control the quantity of direct sun entering the space. Casey cited a metric called “light to solar gain,” explaining that it’s visible light transmission over the solar heat gain coefficient, which tells us the efficacy of the glazing at getting visible light in but keeping the solar heat gain out. Regarding daylight zones, which is the topic of the dissertation he’s working on, he emphasized that we need to control the electric light in those areas in order to gain the full benefits of having the windows.

Lighting designer Galen Burrell of Arup said LEDs aren’t threatening daylighting, but rather represent a huge opportunity to integrate it with SSL to achieve really successful designs. He said good daylighting depends on three parameters: comfort and well-being, visual interest and delight, and energy and cost. But Burrell said there’s so much focus on the last parameter that it’s easy to lose sight of the other two, which lighting designers tend to consider the primary drivers of daylighting. He noted that lighting accounts for between 20% and 25% of a commercial building’s energy consumption, so reducing it will significantly reduce carbon emissions. But Burrell explained that there’s a balance that needs to be struck between too much daylight – which increases heating and cooling costs – and too little. He said as energy savings from daylighting shrink due to the increasing efficacy of LEDs, the other factors – such as comfort, wellbeing, and productivity – will take on greater importance.

Jennifer Scheib of the University of Colorado at Boulder looked at daylighting from the perspective of zero-energy buildings, focusing on three case studies. She said that based on her personal experience, it’s definitely possible to achieve zero energy in a building at no added cost in a typical marketplace. Scheib noted that tubular daylighting devices can be an important strategy because they allow good daylight distribution, plus because of the smaller roof penetration they can be embedded in a ceiling plenum, and the heat gain can be controlled better than with a typical skylight. She explained that LEDs are very well-suited for working with daylighting, because they allow for rapid changing of the conditions and can be dimmed and turned on and off at high time resolution. So in that sense, Scheib said, LEDs are enabling the use of daylighting for additional benefits, and “there are probably many creative ways that we're going to see that play out in the near future.”

Kevin Van Den Wymelenberg of the University of Oregon talked about designing buildings for humans. Emphasizing that most buildings are for people, he made the point that lighting technology disrupts architectural design. Van Den Wymelenberg noted that in the early part of this decade, there was a lot of research on daylighting from an energy perspective, but the stories that emerged were much broader than that. He cited a Lighting Research Center analysis that found a 20% decrease in the price of commercial real estate when the space didn’t have access to daylight and views, and other studies that showed benefits to such things as productivity, classroom performance, retail sales, and the microbiome. Van Den Wymelenberg said one of the exciting things about LED lighting is that it can be spectrally tuned to mimic daylight or blend better with it.