Workshop Presentations and Materials

Over 1,500 researchers, manufacturers, industry insiders, academics, and other lighting stakeholders from the U.S. and abroad gathered for DOE’s 19^th annual Solid-State Lighting Workshop, held January 31–February 3, 2022. The workshop, a cornerstone of DOE SSL program planning, was once again cosponsored by the Illuminating Engineering Society (IES), leveraging the duo’s long-term partnership to advance the quality and efficiency of lighting through engineering, science, design, and collaboration. For the second year in a row, the workshop was held virtually and with free registration, and attendance nearly doubling from 2021.

With an increased emphasis on discussion, speakers and participants engaged in robust conversation via live chat to share progress, challenges, and ideas, pondering questions such as: How are industry and research pushing the boundaries of technology development in advanced lighting system efficiency, quality of light, controllability and connectivity, productivity and health, and overall environmental footprint? What stands in the way of further development and greater deployment? What should DOE prioritize with its future research?

This year’s agenda offered the most expansive set of topics yet to inspire speakers and participants alike. Along with important advances in materials and manufacturing, panels focused on developments with non-visual physiological effects of light, germicidal ultraviolet lighting, building integration, and sustainability. Next-generation lighting also played a bigger role in the 2022 workshop, with U.S. Secretary of Energy Jennifer M. Granholm announcing live the winners of the L-Prize Concept Phase, and a timely discussion on promoting and fostering the future lighting workforce through effective lighting education, technical training, and diversity.

MONDAY, JANUARY 31, 2022

Brian Walker, manager of the DOE Solid-State Lighting Program, welcomed attendees to the workshop and introduced Ramachandran Narayanamurthy, the new director of DOE’s Emerging Technologies Program, who provided brief remarks. Brian Liebel, IES director of standards and research, described how the IES’s mission of “improving life through quality of light” and their activities meld with the DOE SSL program and especially the annual workshop.

Brian Walker wrapped up the introductory portion with an update on the “state of the DOE SSL program.” He outlined the impact DOE-funded projects have made in the market; the program’s priority research areas of platform technology, integration and validation, and lighting science — all supporting the goal of efficient and flexible lighting that supports health, productivity, and well-being; and emerging research areas to be explored in several workshop sessions. Walker urged attendees to take advantage of the many discussion opportunities during the workshop and emphasized that sharing feedback with DOE helps to shape the Lighting R&D Opportunities roadmap, widely referenced by government, industry, and academia and informing all DOE funding opportunities and project selections. The 2022 Lighting R&D Opportunities report was released during the workshop.

KEYNOTES

Keynote talks from two leading lighting manufacturers set the stage, starting with Acuity Brands, the largest manufacturer in the United States. Acuity president Trevor Palmer discussed current and future trends in lighting and as well as energy savings and carbon reduction goals for major U.S. businesses, highlighting the role of efficient and controlled lighting in meeting these goals. Oleg Shchekin, chief technology officer at Lumileds, emphasized that ongoing investment in LED technology will be necessary to reach the next levels of luminous efficacy, digital lighting can support new lighting value in terms of human-centric lighting and visual performance, and micro-LED developments can be leveraged to support these efforts.

ENERGY SAVINGS FROM LIGHTING APPLICATION EFFICIENCY

DOE advisor Morgan Pattison introduced the first panel, which explored how new capabilities of LED technology enable energy savings beyond just improved source efficiency. Pattison described how LEDs enable improved optical control, intensity control, and color control, which can reduce lighting energy consumption and improve functionality of lighting.

Raj Bhagavathula of Virginia Tech Transportation Institute presented on the additional energy savings and performance improvements in roadway lighting applications. LED technology improves optical directionality compared to previous roadway lighting technologies such as high-pressure sodium (HPS). LED lights can be engineered to provide light just on the roadway with optimal surrounding light level to enable visibility of pedestrians, crosswalks, and potential roadside hazards. Optical distributions optimized for curved roads can also be achieved with LEDs, reducing the number of poles to install, the number of lights, and the total amount of light. In terms of spectral control, Bhagavathula also presented research showing that LED 4000K spectrum improved detection distance compared to other LED correlated color temperatures (CCT) and HPS lighting, representing an improvement in lighting functionality. In parking structures 5000K CCT LED was preferred for safety, comfort, and parking space detection compared to 3000K LED and HPS lighting. Regarding intensity control, Bhagavathula described how, with roadway lighting, there is typically a safety asymptotic benefit with increasing light levels and roadway lighting guidance can be set to meet these minima, reducing energy consumption and ecological side effects. He added that adaptive lighting, reducing light levels later in the night or when no one is present, also leverages the ability to control LED intensity. Bhagavathula concluded by stating public perception is generally favorable to adaptive outdoor lighting and described research efforts focused on improving its performance and application.

Christoph Reinhart of Solemma and the Massachusetts Institute of Technology presented on lighting application efficiency and daylighting. He described the utility of photons that are emitted upward and are seen by satellites, with none reaching the human eye. In a crowded sports stadium, he said, potentially almost all the electric light illuminates a surface and connects with vision. In an empty parking lot, at night with lights on, none of the light serves a purpose by illuminating a surface for vision.  Reinhart said within the context of building design, daylighting can increase building value while reducing energy consumption if the utility of the daylight is maximized; a building’s façade and orientation must be considered along with glare at certain times of the day and year. The controllability of optical direction and intensity of LED light sources means they can be used to supplement and enable daylighting in buildings and support occupant health. In addition, Reinhart said, the efficiency of LED lighting means that photovoltaic yield for a building footprint can reach net zero energy consumption with the building electrical load.

NON-VISUAL PHYSIOLOGICAL RESPONSES TO LIGHT

The next panel session was led by George Brainard, director of the Light Research Center at Thomas Jefferson University. He provided background on the history and state of understanding of non-visual physiological responses to light as well as background on the discovery of the melatonin action spectrum, and supported the use of lighting practices that follow evidence-based lighting guidance as codified by the IES and the CIE (International Commission on Illumination).

Melissa St. Hilaire of Harvard Medical School spoke on the topic of spectral sensitivity of physiological responses to light, comparing different research techniques for determining responses to different light spectra and comparing and reconciling responses in shorter duration studies to longer duration exposures. She described the three primary effects of melatonin responses to light: suppression of pineal melatonin; production circadian phase resetting; and acute alerting. St. Hilaire concluded that there can be significant cone photoreceptor contribution to melatonin suppression earlier in a light exposure. Over time, she added, the contribution of intrinsically photoreceptive retinal ganglion cells (ipRGCs) are primarily responsible for melatonin suppression, thus melatonin responses to light by different photoreceptors in the eye are a function of light exposure duration.

Samer Hattar from the National Institute of Mental Health (part of the National Institutes for Health) reminded the audience that the daily changes in light levels from day to night are significant and a fundamental signal in the environment, and that our eyes provide conscious and subconscious perception of light. He described research results in rodents that led to the discovery of ipRGCs by clearly showing they are responsible for maintaining circadian rhythms. There are multiple types of ipRGCs, he added, and ipRGCs and rods and cones are the only photoreceptors in the eye. Hattar explained how ipRGCs provide signals to other pathways in addition to the suprachiasmatic nucleus, the brain’s central timekeeper. Light can also directly influence mood, cognitive function, energy and metabolism, sleep, and alertness through other direct pathways.

John Hanifin of Thomas Jefferson University rounded out the panel discussion with a talk on optimizing lighting for human health. Research results have shown that blue enriched light suppresses melatonin secretion and shifts the onset of melatonin production. With mice, blue-enriched LED lighting resulted in lower dietary and water intake and lower animal growth rate, amplification of the melatonin signal, and slower metabolism, all factors associated with improved animal health and well-being. He added that different lighting on research animals may influence scientific outcomes that are being studied. Hanifin described a new DOE-funded R&D project with a team from Thomas Jefferson University, Tulane University, and Rensselaer Polytechnic Institute. The objective is to clearly establish a link between lighting conditions and human health. The two key questions for the research are 1) What are the physiological impacts of indoor light on human and health and well-being? and 2) Can the impacts be sustained in less controlled circumstances? The project will quantify characteristics of human metabolic, endocrine, and sleep physiology affected by tunable solid-state lighting versus fluorescent lighting, first in a controlled laboratory study and then a naturalistic study. The onset of melatonin production, amplitude, and duration of melatonin production, glucose, insulin, leptin, and cortisol levels will be monitored in the study along with sleep latency and efficiency. The findings will be used to support evidence-based lighting guidance and practices.

Both Day 1 and Day 2 of the workshop concluded with interactive discussion sessions from a subset of  DOE-funded research projects. Attendees could engage directly with lead researchers on the topics of lighting application efficiency, advanced lighting at Pacific Northwest National Laboratory, LED manufacturing, and OLED materials (Day 1) and LED materials and down-converters, OLED light extraction, germicidal ultraviolet (GUV) measurements and reliability, and OLED manufacturing (Day 2).

The R&D highlight sessions were a gateway to the workshop’s annual poster forum, which this year hosted the work of more than 50 researchers. During the workshop, attendees were encouraged to visit the virtual poster forum at their convenience, review the research via poster PDF or video, and contact lead researchers directly with questions.

TUESDAY, FEBRUARY 1, 2022

NEXT-GENERATION LIGHTING PROFESSIONALS

Day 2 of the workshop began with a stimulating session devoted to promoting effective lighting education, technical training, and diversity in the lighting workforce. First, the two grand prize winners of the 2022 Student Poster Competition and future members of the lighting workforce – Shruti Hariyani of the University of Houston and Hannah Moon of the University of Hawai’i at Mānoa – presented their research on advancing human-centric lighting and using electroretinograms to characterize the retinal response of endangered Hawaiian seabirds to different light spectra, respectively. These winners, along with honorable mention students from Penn State University, Rensselaer Polytechnic Institute, and Texas A&M University, also participated the virtual poster forum.

The second part of the session, moderated by Brienne Musselman of IES and Lisa Pattison, a DOE lighting program advisor, convened a panel of experienced lighting professionals who shared their insights for shaping the industry’s next generation. Bernadette Boudreaux of the DesignLights Consortium began by recognizing that most lighting professionals, including herself, have somehow “fallen” into the field rather than specifically choosing it. In sharing her path into the lighting industry, Boudreaux offered suggestions not only to promote the lighting industry and attract talent but also to change the lack of diversity in the field. She reviewed current diversity, equity, inclusion, and respect (DEIR) initiatives and preliminary plans for forming a minority serving institution (MSI) lighting incubator.

Kenneth Connor, a professor emeritus from Rensselaer Polytechnic Institute (RPI), talked about his DEIR efforts in engineering through formation of the Inclusive Engineering Consortium. The IEC has a “super department” model in which colleges and industry partners come together to share resources and support to improve science and find success through diversity and the creation of equitable partnerships. Connor presented an “illumineering curriculum” developed at RPI that helps students better understand the path to a job in lighting and noted the key need for hands-on learning and early engagement with students at the compulsory level. One program that has helped meet this need, he said, is an “engineering ambassadors” program in which students become teachers of the next level down in education — a chain of learning ranging from university faculty to elementary school students.

While Connor focused on early educational initiatives, Bob Davis of Pacific Northwest National Laboratory talked about university-based lighting education. Davis discussed the variety of college degrees that emphasize lighting, including architecture, architectural engineering, interior design, and theater. He also pointed out that colleges have many opportunities for lighting professionals to participate in short courses, seminars, and even for-credit classes in lighting. Davis echoed Boudreaux’s concern about the lack of diversity in lighting and shared his experiences developing a lighting class curriculum and teaching (virtually) at Tennessee State University, a historically black university.

Finally, Yulia Tyukhova, an independent researcher and former chair of the IES Emerging Professionals program, explained how the EP program helps provide support and opportunities to new lighting professionals, from scholarships and continued education to interning and networking opportunities with peers and seasoned professionals. Along with benefitting those entering the lighting workforce, the EP program benefits the industry and society as it promotes growth of the workforce and engages new talent to help solve the industry’s challenges together.

ADVANCES IN LED MATERIALS AND DEVICES

DOE advisor Monica Hansen moderated a panel that explored the latest innovations in LED device architectures and materials developments, with concepts such as digital light sources, ultraviolet C (UV-C) LED advancements, pushing quantum dot (QD) performance at higher drive conditions, and the use of predictive modeling to discover new phosphor materials.   

Wouter Soer of Lumileds presented on the development of a digital light source for adaptive lighting systems, part of a DOE-funded project led by Rensselaer Polytechnic Institute. Soer said a full function dynamic light source will provide tuning over a wide range of beam angles and spectra, but the challenges include controlling hundreds of pixels, steering the light, and spectral control. These digital light sources can leverage development of integrated circuit technology used for local dimming and full array backlights in the automotive and display industries. He added that further advancements in projection optics for beam steering and improved approaches to color mixing have led to early prototypes being tested in advanced lighting systems. Initial applications of the digital light source will be based on conventional lighting performance criteria, but advanced applications with value beyond traditional scope of lighting will emerge (e.g., human health and well-being, building space flexibility, and aesthetics/artistic design).

Ling Zhou from BOLB spoke about the challenges and current status of UV-C LED emitters, specifically approaches to reduce the p-side optical absorption. There is a tradeoff of increasing the light output or reducing the LED voltage due to the low carrier concentrations and high absorption in the high aluminum-containing p-type layers used for the deep UV wavelengths. BOLB developed a strained, thin p-AlN (aluminum nitride) cap layer to create a very high charge density on p-AlN surface, thus creating a high transparency p-side with good working voltage, which has led to a threefold improvement in UV-C LED device efficiency. Zhou highlighted areas for future device improvement, including more reflective contacts and eliminating total internal reflection. Improved package materials that can better handle the thermal load of UV-C LEDs and can withstand the high energy photon flux are also needed to improve power output and lifetimes.

Ilan Jen-La Plante of Nanosys described work on a DOE-funded project improving cadmium-free QD lifetimes under elevated temperature and excitation flux for use in LED applications. The research involves developing a better understanding of the QD photothermal degradation mechanisms by controlling the QD structure with synthetic modifications followed by correlation of QD photophysics to the performance. Jen-LaPlante said the team found the composition control of the InP/ZnSe core/shell interface can promote increased transient hole trapping that leads to long radiative lifetimes and slow photoluminescent risetimes. Maximizing the less damaging Auger electron excitation process improves QD lifetime under high flux excitation.

Finally, Jakoah Brgoch of the University of Houston illustrated how to use data science to predict the optical properties of phosphors. The first challenge, he said, is obtaining a large data set of the phosphor’s physical parameters required for use in LED lighting (e.g., centroid shift, bandgap). The next step is developing a physics-based feature set for machine learning. Brgoch showed an example of machine-learning models constructed to predict centroid shift and bandgap. Plotting the results of the machine-learning predicted centroid shift and bandgap for unknown compounds to provide a high-level screening for yellow phosphors. Beyond machine learning, he said, there is an opportunity to realize accelerated phosphor discovery using robotics for materials synthesis experiments.

ADVANCES IN OLED MATERIALS

In this panel, moderated by Lisa Pattison, four OLED experts discussed recent results and directions for future materials research. Kicking things off, Maria Vasilopoulou of the Institute of Nanoscience and Nanotechnology at the National Centre for Scientific Research Demokritos (Athens, Greece) presented her work on blue OLEDs with below-bandgap electroluminescence. Through the application of an interface exciplex host combined with a high mobility hole transport material, her team was able to realize state-of-the-art blue OLED performance of 41.2% external quantum efficiency (EQE) at low operating voltages while increasing the device lifetime by sevenfold and reducing efficiency roll-off. This work demonstrates the potential for using simplified, alternative device structures for the fabrication of efficient and stable blue.

Michele Ricks of EMD Electronics discussed the use of host and transport materials to optimize OLED devices for the best performance. Research is under development to address recent needs: hole transport materials (HTMs) for reduced crosstalk; electron transport materials for charge balance and efficient, stable devices; and pre-mixed hosts for ease of manufacturing. Ricks shared impressive results when comparing their new materials to industry standards including nearly doubling lifetime of blue devices while simultaneously lowering voltage in blue devices with HTMs and pre-mixed hosts for green devices offering improved lifetimes.

Tommie Royster of R-Display and Lighting shifted the conversation to emitter development, where his company has been developing hybridized local and charge-transfer (HLCT) blue emitter materials for OLED lighting. These materials have charge transporting processes and low voltage useful for OLED devices, and they exhibit short excited state lifetimes (in the range of nanoseconds) which should allow exceptional stability by reducing the non-radiative processes associated with long-lived excited states. The HLCTs Royster is developing are metal-organic framework molecules with bipolar delocalization properties that enhance stability (since the energy is dispersed across larger area of cluster framework); are porous, allowing for fast electron and ion diffusion; and are structurally flexible for electronic tuning.

Chihaya Adachi of Kyushu University (Fukuoka, Japan) presented recent results on TADF and hyperfluorescent blue emitter materials. He echoed the importance of short excited state lifetimes for device stability and discussed how excited states can be engineered for efficient thermally activated delayed fluorescence (TADF). To achieve short excited state lifetimes, slight modifications in the molecular structure can be made to lower the singlet-triplet energy gap and increase the rate of reverse intersystem crossing for quick upconversion of the triplet states. He illustrated this mechanism with data showing a 30x improvement in lifetime resulting from excited state engineering. Adachi next turned his focus to hyperfluorescent materials, which are known for their high efficiency, low cost, and high color purity. He described a new sky blue hyperfluorescence emitter system that showed EQE >40% and LT95 ~13 hours @1000 nits in 2-stack tandem devices. By optimizing the device architecture and introducing a mixed host system, the researchers were able to extend the device lifetime to 67 hours, showing the usefulness of mixed hosts in balancing electron and hole transport inside the emitting layers for optimal performance.

BREAKING THROUGH TO NEXT-LEVEL LIGHTING PERFORMANCE

Mark Lien of IES moderated a panel examining lighting breakthroughs made possible by SSL technology. Jim Gaines of Signify presented the company’s Philips-branded, super-efficient, screw-in lamp, characterizing it as a “big leap forward in A-lamps.” Currently sold only in Europe, the lamp meets the European Union’s Ecodesign Class A requirements at 210 lumens per watt (lm/W), well beyond the 115 lm/W of typical high-efficacy LED replacement lamps. Gaines referenced the considerable progress  made since Philips won the first L-Prize® award in 2011. At that time the 90 lm/W requirement, along with 2700K correlated color temperature (CCT) and 90 color rendering index (CRI), was a huge stretch. Pacific Northwest National Laboratory, Gaines said, continues to test 30 samples of the original L-Prize lamps, which have passed 90,000 hours at 45°C continuous operation and show >90% lumen maintenance and <.003 chromaticity shift. Signify’s new 210 lm/W lamp comes in 3000K and 4000K and has 80 CRI, Rf 85, and Rg 93. He noted, however, that there are tradeoffs in dimmability, CCT, CRI, power quality, mains voltage, stroboscopic effect, light intensity distribution, spectrum, and cost. The product cannot simultaneously be 210 lm/W and dimmable, >90 CRI, 110-volt, directional or small volume, connected, and Energy Star qualified plus meet California Title 20 requirements and retail price targets.

Steve Paolini of Telelumen presented on a different aspect of breakthrough performance made possible by LED technology: programmable tunable lighting systems. He discussed the balance of luminous efficacy and application efficiency, particularly where high emphasis is placed on health and wellness, the ability to replicate actual daylight spectra, and enhanced product appearance. Tunable lighting systems can provide the best spectral power distribution (SPD) for the specific application, hold chromaticity constant with various SPDs, and provide a dynamic experience mimicking daylight. Paolini said the photopic sensitivity curve “leaves out half the visible spectrum,” with relatively lower sensitivity to blue and far-red wavelengths. The differences in human visual sensitivity to different wavelengths, he said, shouldn’t be interpreted to mean that lower sensitivity portions of the spectrum are not important. Paolini also described the importance of far red, especially in color rendition of all human skin tones.

Carol Jones of Axis Lighting addressed the breakthrough potential of SSL-based intelligent lighting systems, focusing specifically on the major barrier to successful deployment and operation of such systems: lack of interoperability. Interoperability is necessary for different parts of a system to work together; interchangeability requires that parts of a system can be exchanged or replaced and still work. The system, Jones explained, consists of hardware + firmware + software. The Internet of Things (IoT) refers to device data + communication + analytics to the dashboard. “Plug and play” means components work together without custom programming. While IoT lighting is not new, she said, it has not been interoperable to date. This lack of interoperability makes IoT lighting “not super comfortable” for the customer in that it is not easy to configure, commission, maintain, and update such systems. Two developments that will help provide bases for interoperability are D4i drivers using DALI open-source standards for data transfer and the Zhaga Book 20 sensor interface.

Nate Mitten of Kimco Realty focused his presentation on parking lot lighting controls. Kimco owns shopping centers and mixed-use real estate assets with over 400,000 managed parking spaces nationwide, and the company is responsible for almost all the outdoor lighting. Mitten said as of 2021, Kimco has converted 350 sites from zone-level scheduling and fault monitoring to “controls-ready” LED fixtures. They are also monitoring performance of 15 fixture-level control projects installed from 2019 to present. He said the company has increased their 2030 greenhouse gas reduction goals from 30% reduction to 45% relative to 2015 levels. However, they also have experienced more security concerns, causing camera installations to increase 600% from 2019 to now. Operational awareness and resilience are key goals, Mitten said. Energy savings from fixture-level controls retrofits over the 15 sites averaged 35% to date, with a range of 5.6% to 47.6%. Those with lower energy savings already had zone-level controls. Mitten estimates more precise and reliable occupancy detection enabled by connected outdoor lighting systems, image sensors, and software analytics can add 10% to 20% more system-level savings.

WEDNESDAY, FEBRUARY 2, 2022

LIGHTING SUSTAINABILITY: A CRADLE-TO-CRADLE DISCUSSION

Day 3’s opening session, moderated by Kate Hickcox of Pacific Northwest National Laboratory (PNNL), focused on the challenges and opportunities to reduce the environmental impact of LED lighting across its life cycle.

Session keynote Lindsay Baker of the International Living Future Institute (ILFI) began with a call to change how we see the world, and how we see the future. Instead of working toward a world that is simply a less-bad version of the one that we currently have, we must ask, “What does good look like?” Baker urged the design of buildings and products that sequester carbon, remove toxins, support health and well-being, and give more than they take. She reviewed some of the ILFI programs that support the approach to making a positive future, including certifications, transparency labels and education, and ILFI-hosted events. Baker described the Living Product Challenge (LPC), a powerful and holistic framework that addresses material health, life-cycle impact, and social equity by looking at a product’s footprint (the negative impact) as well as the “handprint” (the positive impact). She ended her talk by asking, “How do we go from possible to scalable?” According to Baker, there is no time to show successes product by product — we must move quickly to change policies and regulations so that sustainable products and buildings are not just for those who can afford it, but for everyone.

Roger Sexton of Stoane Lighting presented an overview of creating a circular economy in the lighting industry. Using the Chartered Institution of Building Services Engineers (CIBSE) TM66 methodology as a framework, he gave real-life examples of Stoane Lighting’s circular approach to design, manufacturing, and re-manufacturing at end of life. TM66 is a circular economy assessment method questionnaire that walks through a product’s life cycle and materials use and considers product design, manufacturing, materials, and the product ecosystem. The key to circular product design, Sexton said, is to keep the products and materials in use for as long as possible. Manufacturers can tie into circularity through recycling, finding ways to use recycled materials in the design process and design opportunities to recycle parts and materials at end of life. Manufacturers can also support the circular economy by incorporating additive manufacturing and modular design, and repurposing waste. The product ecosystem can support circularity by repurposing or repairing both packaging and products. Sexton summed up the talk with a beautiful image of a gallery in Amsterdam’s Van Gogh Museum, lit entirely with remanufactured and reused Stoane Lighting luminaires.

James Salazar of the Athena Sustainable Materials Institute provided insight and understanding of life cycle assessments (LCAs) and Environmental Product Declarations (EPDs) for the lighting industry. The lighting industry has not traditionally adopted the use of LCAs, Salazar said, but as the industry focuses more on embodied carbon impacts, the role of LCAs will become more important. Salazar gave a primer on LCAs and EPDs and some of the other rules, requirements, and “functional units” that are part of that assessment. While the process of performing an LCA is the same for every industry, he said, the lighting industry has its own product category rules (PCRs) that harmonize with the lighting LCA. LCAs will provide information on the product’s impact on global warming, acidification, ozone depletion, smog, and other critical effects. Salazar discussed some market drivers for the LCA and EPD processes, including LEED green building systems and “Buy Clean” legislation at the state level. He concluded it is increasingly critical that we understand our embodied carbon impact in the lighting industry, and LCAs are an important tool to give us that understanding.

Sustainability professional Mike Johnson gave a talk titled, “Building for a Net Positive Future, Now!” which addressed the challenges and promises of net positive products. He began with a daunting reminder of why work in lighting and sustainability is so critical right now: In January 2022 the Earth’s atmospheric concentrations of CO₂ were 416.71 parts per million (ppm). The “tipping point” at which runaway climate change is possible is 400 ppm, which was hit in 2016. This translates into worrisome and record-breaking temperatures. In 2021, Johnson added, weather or climate catastrophes in the United States totaled $22 billion dollars. And by 2100, the Earth’s population is projected to reach 11.2 billion. To ensure everyone on the planet has the resources needed to thrive, we must take advantage of all sustainability opportunities — and designing around net positive products or projects is a substantial opportunity. Johnson emphasized the urgency not only to mitigate hidden costs, but also identify net positive goals, and he concluded with specific suggestions and actions that could be taken to achieve a positive future now.

ADVANCED MANUFACTURING TECHNOLOGIES

Monica Hansen moderated the next panel, which explored various manufacturing processes and tool innovations in the LED lighting ecosystem, including advances in sustainable materials and processes to advance the circular economy and new tools for development of novel lighting form factors.

Aaron Smith of Finelite began by highlighting the need to develop technology that is recyclable, reusable, and free of harmful chemicals. Encouraging materials transparency reporting for lighting products is an important first step in eliminating toxic materials. Smith also discussed recyclable and sustainable materials and designs that can be used to feed the circular economy at the end of life, starting with these suggestions: make optics, lenses, and other components out of ocean plastics; explore trash recovery for large scale 3D printing and extruding; and develop U.S. based natural supply chains like bamboo, algae, molded pulp for use in new lighting technologies.

Lars Waumans of Signify described the viability of 3D printing for mass production of luminaires, with the ability for mass customization with tailored designs in a sustainable production technology. 3D printing, Waumans said, allows custom shapes, dimensions, color, textures, and light technical specifications without requiring the investment in tooling and the subsequent tooling lead times. He added that 3D printing supports the circular economy via its on-demand benefits that avoid waste in transportation, surplus of stock, and unused materials. It also leads to reduced emissions, enables local production, and results in lightweight materials in lighting fixtures, all of which translate in a carbon footprint reduction over full product life. Waumans concluded by highlighting the challenges for larger penetration of 3D printing in lighting products, such as developing cost-effective printing of metal parts (heatsinks) and improving 3D printer features to print continuously and effectively.

Shifting gears, Drew Hanser of Veeco Instruments examined manufacturing advances for cost-effective micro-LED epitaxy. Micro-LED technology has the potential to be a mainstream display approach over the next decade because of superior performance, but cost is the biggest barrier to adoption. MOCVD (metal organic chemical vapor deposition) improvements impact the top three cost reduction drivers for micro-LED: die size reduction, wafer size increase, and reduced transfer cost. Improving the performance of MOCVD system capability is critical to impacting these areas. Hanser said developments in high performance epiwafers (wavelength uniformity, defectivity), scaling to mass production of 200mm and 300mm wafer sizes, and the compatibility of these micro-LED wafers with silicon wafer fabs are all critical to enable cost effective micro-LEDs.

Eugene Chow of PARC rounded out the panel by describing a novel chip printing technology for high chip count systems. This new platform for integrating chips is being developed on a DOE-funded project focused on enabling economical production of thin lighting sheets. Chow said the benefits of this manufacturing tool include high throughput, low cost, and heterogeneous placement of small chips (10–500 microns) in a digital approach to realize custom patterns and rapid prototyping, with a cost structure independent of the number of devices. The prototype printing tool uses directed electrostatic micro-assembly to generate electric force fields to individually direct chips in parallel to target locations, allowing for advanced lighting layouts with multiple LED types to enable spectral tuning.

DIFFUSE LIGHTING PANELS

DOE advisor Norman Bardsley moderated a panel examining the status of diffuse lighting fixtures based on OLEDs and edge-lit LEDs, with research aimed at improving the performance. The potential of using quantum dots in planar sources was also assessed.

Jeff Spindler of OLEDWorks pointed out that OLED structures are, by nature, surface area light sources. They are thin and flexible, with active layers less than 1 micron thick. The organic layers can easily be stacked to produce higher brightness and longer lifetime with any color. These qualities, Spindler said, are being exploited in segmented rear automobile lights as well as in ultra-thin luminaires with high color quality. Spindler also provided the status of vapor thermal evaporation, the traditional deposition technique for organic materials, and discussed alternative approaches using printing techniques or roll-to-roll processing that may lead to cost reductions. Research priorities, he said, include higher light extraction efficiency, lower cost, higher throughput encapsulation technology, and the integration of flexible panels with robust mechanical, electrical, and thermal connections.

Claire Arneson from the University of Michigan described research on the use of sub-electrode micro-lens arrays (SEMLA) to enhance light extraction from OLED panels. In a typical application, an array of closely packed hemispherical indents is etched into the substrate glass with a pitch of about 10 microns. A high-index polymer is spun to planarize the substrate surface and allow deposition of the anode and organic layers. The design of the system was guided by complex optical simulations. Arneson said experiments with multi-stack OLEDs were carried out both at the University of Michigan and OLEDWorks. The results demonstrate that most of the light from the emissive layer reaches the substrate. The combination of SEMLA and an external micro-lens array should lead to substantial improvement in OLED efficiency.

Sergey Vasylyev of Lucent Optics discussed the development of flexible waveguides lit by an array of LEDs along one or more edges. One major operational advantage over OLEDs, he said, is that light extraction is much simpler. Losses due to trapping in the waveguide can be less than 2%, and the overall optical efficiency of the device can reach 88%. Light extraction can be achieved by printing drops of ink onto inexpensive plastic films. Light is spread across the panel with uniformity of around 90%. Vasylyev said the mixing is so efficient that color tuning can be achieved by the inclusion of LEDs with different spectral distribution. Alternatively, the waveguides can be patterned to achieve segmented emission. He concluded the combination of LEDs with optical waveguides provides high optical performance and low material intensity, while supporting sustainable manufacturing and lowest cost potential.

Homer Antoniadis of Nanosys gave a broad survey of the roles of quantum dots in displays and lighting. The ability of quantum dots to provide a narrow distribution of light at any wavelength within the visible spectrum enables a powerful tool in spectral engineering. This capability has been demonstrated in quantum-dot color conversion (QDCC) of blue LED light to improve the color control in many LCD displays. Panels embodying quantum dots are offered by all the leading TV manufacturers. Looking forward, Antoniadis said, inkjet-printed or photolithography-patterned QDCC technology will also improve OLED and microLED displays. Applications in lighting are still in the development phase, he said. Research is underway at Nanosys to improve the stability of quantum dots within LED packages and to use QDs in electroluminescence as light sources in diffuse lighting panels.

DISINFECTION: WHAT HAVE WE LEARNED ABOUT GUV AND OTHER METHODS?

Alex Baker of IES moderated the next panel, which discussed GUV technologies and applications, updates on planned research and standards, and energy implications and research opportunities for GUV technology, namely the development of ultraviolet C (UV-C) LED technology.

Dianne Poster from the National Institute of Standards and Technology (NIST) began with an overview of GUV applications, explaining the science of UV in disinfecting for pathogens, the types of sources that provide UV, and the applications in which they are used. Poster addressed both air and surface disinfection treatment as well as potential energy savings of using UV inside ducts of HVAC systems.

Gabe Arnold from Pacific Northwest National Laboratory introduced a new GUV research and development program that PNNL is implementing on behalf of DOE. Arnold stated the program is needed due to the current “wild west” landscape of GUV technologies, and he described the product testing and field evaluations that will be conducted through the program. He also discussed the energy-implication focus of the research, the energy-related research questions the program will aim to answer over time, and some preliminary energy savings claims of GUV that support the need for more research and validation.

Cameron Miller from NIST gave an update on new and under-development standards for measuring GUV performance. He discussed NIST’s collaboration with IES and IUVA (the International Ultraviolet Association) and the standards these organizations are jointly working on. IES/IUVA LM-92, Miller said, is one standard that will provide the method for measuring performance of LED-based GUV sources. He then covered the NIST calibration service, a new standard under development to measure performance of GUV excimer lamps, a standard to measure application distance radiometry in near-field applications, and issues with UV measurement detectors. Miller concluded with an update on the new IES RP-44 Recommended Practice, and other standards under development from organizations including ASHRAE (the American Society of Heating, Refrigerating, and Air-Conditioning Engineers), IEEE (the Institute of Electrical and Electronics Engineering), and the CIE.

Ed Nardell from Harvard Medical School provided a different perspective on GUV, as a pulmonologist who has researched and used UV technology for decades. He explained transmission methods of respiratory diseases including SARS-CoV-2 (coronavirus) and why GUV is an effective technology for reducing airborne transmission. Nardell shared data from a study where GUV reduced the spread of measles in classrooms and then discussed what is known currently about the effectiveness of GUV relative to ventilation and the associated energy and cost implications. GUV, he said, can be much more cost effective and energy efficient than equivalent ventilation. In addition, Nardell explained different types of GUV fixtures, the importance of air mixing for GUV effectiveness, and the potential of far UV-C as a safer wavelength to deploy GUV, providing information on a pilot study underway by the Clark County School System in Las Vegas, NV.

Mike Krames of Arkesso concluded the session with a talk on the rapid development of UV-C LEDs. Though UV-C LEDs are currently less efficient than incumbent low-pressure mercury, Krames stated that once the advantages of LED technology are accounted for (etendue, directionality), they can nearly compete with the incumbent in some applications. Krames presented a roadmap for UV-C LEDs that predicts rapid improvements in performance and reductions in cost over time that would mimic the progress of blue light LEDs a decade ago. He elaborated on the current technical challenges and how they can be overcome and also expressed the need for continued research and development funding.

INNOVATIONS IN DISPLAY ARCHITECTURE FOR IMPROVED ENERGY EFFICIENCY AND PERFORMANCE

Wyatt Merrill from DOE moderated a panel exploring the energy savings opportunities with display architectures that can improve efficiency and performance features. Merrill began with a talk reviewing the electricity use footprint for buildings, comparing the size of the various loads of lighting, heating, cooling, appliances, and miscellaneous electric loads such as TVs, monitors, laptops, ceiling fans, microwaves, coffee makers, etc. He pointed out that as current non-electrified end uses convert to electricity (e.g., electric vehicles, replacing gas furnaces with electric), the future electric loads in a building will increase, making it vitally important to improve energy efficiency across end uses for the future.

Bryan Urban of Fraunhofer USA continued by examining the display energy use trends in U.S. homes. Consumer electronics account for 4–5% of U.S. electricity consumption, and approximately 40% of that electricity use is displays-related. Most electricity use from displays, Urban said, comes from TVs and monitors, because portable displays use far less. Overall, he added, TV and monitor electricity use had been trending downward with the adoption of newer, more efficient display technology, though that downward trend in consumption reversed with the COVID-19 pandemic. In 2020, he said, consumer electronics electricity use increased by over 20%, driven by higher usage as people spent more time at home.

Stefan Peana of Dell reviewed power consumption trends as a function of display architecture. He stated that currently, 30–40% of a notebook computer’s power is consumed by the display, and he compared the tradeoffs and benefits of both transmissive and self-emissive display architectures. LCD (transmissive) displays are a mature technology; the newer transmissive technologies using QD enhanced color filters or mini-LED backlight displays are a technical evolution that leverages LCD maturity. OLED is an emissive display technology that provides flexible form factors and large printing format benefit. Micro-LEDs, Peana added, are another emerging emissive display technology that shows promise of higher performance, flexibility, and low power consumption. Micro-LED displays are the key to realizing future optimum high-performance low-power displays, with an 88% reduction in power consumption. Peana said transitional technology such as mini-LED LCDs will help resolve fundamental assembly challenges in support of future micro-LED displays.

David Chen of Power Integrations presented on a novel multiplexed power architecture aimed at improving display efficiency. He began by highlighting the power supply efficiency as a function of the power load; this topology provides 90% efficiency between 10% and 100% of the display power load. The two key aspects of this driver architecture are the gallium nitride (GaN) based primary switch (that reduces conduction losses and switching losses) and the multiplexing stage to achieve single-stage multiple output conversion. For the new single-stage architecture, Chen said, there is only one loss stage compared to the typical two-stage display power supply. This single stage leads to approximately 50% loss reduction and power supply efficiencies of 90%, allowing more efficiency overhead to design the overall display system to meet Energy Star Display Specification requirements.

Bob Karlicek from Rensselaer Polytechnic Institute rounded out the session with a forward-looking talk on display-lighting fusion in the form of virtual windows. He reviewed some case studies of the use of virtual windows in hospital settings and the impact on patients. In general, he said, patients in intensive care units liked virtual windows better than existing windows. Karlicek then shifted gears to consider how a building’s energy consumption could be reduced with virtual windows. Windows are a significant source of building energy loss; windowless buildings could be about 30% more energy efficient. Karlicek ended with a review of the current state of display technology and its performance in a virtual window application.  

Day 3 of the workshop ended with an hour-long topic table session segmented into two 30-minute portions. Each portion offered attendees a choice of five specific lighting topics to participate in small-group discussion. Questions to consider were provided for each topic, and attendee input was collected to guide planning for future DOE and IES research activities. The 10 topics were:

• Lighting Workforce Opportunities
• New Lighting Metrics
• Germicidal Ultraviolet Lighting
• LED Materials and Devices
• Advanced Luminaires and Systems
• Manufacturing and Sustainability
• Lighting Application Efficiency
• Physiological Responses to Light
• OLED and Diffuse Light Sources
• Lighting System Data and Grid Interactive Lighting

THURSDAY, FEBRUARY 3, 2022

TAMING ADVANCED LIGHTING SYSTEM COMPLEXITY: A CALL TO ACTION

The final day of the workshop began with a session helmed by Ruth Taylor of Pacific Northwest National Laboratory. The session looked at challenges with configuration, commissioning, and maintaining control settings over time—barriers that keep us from future integration with other building systems. Panelists focused on the need to develop a clear and concise sequence of operations (SoO) as an important solution to many of the communication challenges plaguing connected lighting system installation and configuration. Taylor also reviewed how DOE is analyzing current configuration complexity issues and shared thoughts on how to approach possible solutions. 

Session keynote Mike Skurla of Radix IoT identified the current industry quandary with connected lighting systems — they lack consistency, making it very difficult for owners and users to take advantage of all these systems have to offer. Skurla summarized the state of the industry as complicated and inconsistent by identifying the many ways proprietary design weakens consistency: proprietary hardware, proprietary setup, proprietary communication, proprietary service, and so on. He emphasized that without solving this problem, the lighting industry will be left just to the lighting, missing all the potential these new connected lighting systems have to offer.

David Ghatan of CM Kling + Associates stated that an SoO or controls narrative provides an important first step in seeing that all those involved in a project align their expectations so that subsequent design and implementation decisions advance toward the same goal. He stressed the importance of communication, citing it as the cause of most pain points in the lighting control system design process.

Charles Knuffke of Wattstopper provided an overview of the construction process, the manufacturer perspective, and how all the players work together for an SoO. He called the SoO a “must-have document” that identifies in detail the level of complexity of the job up front. The SoO pinpoints key systems in the installation, how these systems solve owner needs, and which systems will work with each other and in what way. Knuffke said developing an SoO at the start of a project identifies roles and responsibilities and promotes communication among the key players, especially as installations become ever more complex, because we’ve seen it over and over: lack of understanding among players has served as a barrier to project success.

Brian Coddington of Chicago Lightworks offered the manufacturer representative’s point of view, reiterating the need for all parties involved to be on the same page—including everything in the contract documents is an important start. Coddington said from his perspective he very often does not see an SoO included, so technicians have to guess what the system is programmed to do. The SoO sets expectations for all parties and can save money on costly callbacks.

Taylor asked each panelist to state the most important item to tackle first. Skurla reiterated the importance of consistent vocabulary as the best starting point to improve communication through the process. Knuffke said system mock-ups are key to setting expectations and making sure everyone involved understands what the system is supposed to do. Ghatan said if all parties can be clear on the sequencing, many pain points would be eliminated. Coddington said timelines are key — too often all those involved to do not have the details at the right time in the process, and the time and money needed to get a system working properly is underestimated.

BUILDING SCALE SYSTEMS INTEROPERABILITY AND INTEGRATION

A panel moderated by DOE advisor Greg Thomson considered how integrating electric lighting systems will result in more efficient application of lighting energy and create value in the improved efficiencies of other building systems by sharing data and improving the occupant experience.

Sarah Safranek of Pacific Northwest National Laboratory described the lab’s ongoing research in the simulation and testing of daylight and electric lighting systems integration for meeting occupant needs for circadian stimulus. She discussed recent changes in circadian lighting metrics from the WELL Building Standard, and an approach to meeting equivalent melanopic lux (EML) and melanopic equivalent daylight illuminance (MEDI) lighting needs through careful design of electric lighting systems with the appropriate spectral power distribution (SPD) to fill in the EML/MEDI gaps when daylight is not available or when its use could result in glare for zone occupants. Safranek pointed to two software programs for analysis (LARK and ALFA) and clarified their pros and cons. She said it was difficult to find suitable SPD data for performing analyses and noted that while the irradiance data from the National Renewable Energy Laboratory was available publicly, it was only available for a small subset of locations for which there is also climate data. Safranek showed that when M/P (melanopic/photonic) ratio is high and blue value is high in the SPD range, the space is better able to meet EML requirements. She also showed the impact of diurnal and seasonal effects on M/P values and provided information about the impacts of orientation on these figures.

Michael Myer, also from PNNL, discussed the lab’s ongoing work with the Integrated Lighting Campaign (ILC) and efforts to better understand the integration of connected lighting systems with connected HVAC systems. Myer emphasized that efficiency savings across multiple building systems are not directly additive but more incremental to overall building efficiency. The ILC first proposed there would be a full-scale lighting system upgrade with an advanced lighting control system (ALCS) and that the HVAC systems would not undergo a physical retrofit but simply integrate their building management systems’ (BMS) controls inputs with the new available ACLS data. Myer showed that HVAC integration alone created a 20%–30% savings when making operational changes only (no hardware upgrades). Consequently, he said, substantial energy efficiency improvements are available to existing BMS-controlled HVAC systems without large-scale financial burden. Myer pointed out these systems were installed in places that had a difficult argument to make for retrofits from a financial return-on-investment perspective based on the building use type; however, HVAC integration alone was able to reduce overall ROI by 30% or more. Myer’s research showed that when manual changes to HVAC setpoints were made, there was interference with operational communications, resulting in the systems not returning to their original operational setpoints. He stated there is a clear need for additional research into software persistence and operational algorithms to prevent this from happening. Myer also qualified the savings and payback schedules by discussing the impact of building use type and size on the costs of system installation and said that more research is needed with respect to appropriate building sizes and building use types for integration.

Kenny Seeton of California State University Dominguez Hills (CSUDH) described the school’s experiences with the installation, operations, and maintenance of integrated lighting and building HVAC systems. Seeton stated the approach to the controls application and shared the results of a recent ALCS retrofit in CSUDH’s primary administration building, completed just prior to the pandemic. The building saw immediate savings from the system upgrades, Seeton said, but it was difficult to control HVAC for multi-room/multi-space HVAC zones, a common difficulty with commercial buildings. CSUDH used lighting sensors to minimize HVAC use for different levels of occupancy as a method of increasing application efficiency. Seeton also emphasized the importance of having clear discussions with general contractors and vendors about the nature of the integration project and the necessity to ensure the delivery of a fully functional system. He also pointed to the importance of establishing a relationship with the organizational IT department to help make the installation and operation of the control systems as seamless as possible. Seeton said ongoing operational activities include simple educational conversations with new occupants in the spaces to ensure they understand how the systems operate and how they can modify the settings when needed. He described the effort required to ensure ALCS installations are fully functional, including the risks associated with having multiple installations and the possibility of having communications interruptions when the building automation and control network (BACnet) is overloaded with too many controls points.

Alexi Miller of the New Buildings Institute (NBI) addressed the current and future conditions for integrating lighting systems with other building systems as they are described and regulated by building codes. He showed that under the most current building codes and standards (the International Energy Conservation Code [IECC], ASHRAE 90.1-2019, and California’s Title 24), there are no interoperability or integration requirements. There are demand response (DR) integration rules (including the amount of load shedding that lighting will be required to contribute to a DR event) and requirements for sensor-based controls that depend on local occupancy and vacancy sensors. In addition, he said, there are required controls interactions for specific systems and DR, but no required, regulated, or proscribed interoperability or integration with other building systems. In the IECC 2019 section C406.4, no more than four luminaires that can be connected in a controls group when they are individually addressable and in a daylight zone, no more than 8 in a controlled group; these lighting controls (including occupancy sensors) must be reconfigurable through digital addressability. Miller described the proposed NBI IECC overlay and code futures, which targets the codifying of nationwide capacity for lighting to participate in DR events, as well as having more rigorous requirements for smart and digital controls, luminaire level lighting control individual addressability, and occupancy and vacancy sensors.

NEW FRONTIERS OF LIGHTING

In the workshop’s final panel, panelists presented visions for the future of lighting technology and opined on the possible transformations from today’s conventional luminaire systems integrated with SSL sources to new and innovative approaches that can reshape lighting technology.

Mark Lien from IES explored how the future of lighting is about the convergence of technologies and services. He discussed the impact of several industry changes, including globalization, carbon metrics, and renewable energy sources. Industry organizations, he said, are working on the globalization of standards. The ASHRAE Task Force for Building Decarbonization was established to address embodied carbon. Renewables will change the energy sector, leading to further electrification as a renewable grid emerges. Lien also reviewed technology trends that impact lighting: LiFi/optical wireless communication is presenting growth opportunities. 3D printing is gaining momentum as a disruptive technology in lighting product manufacturing. New applications such as autonomous vehicles or robots and drones for productivity is leading to a reevaluation of existing lighting requirements. Lien offered several predictions for lighting over the next decade, including that lighting will further miniaturize and integrate into the electrical infrastructure of our buildings, morphing with other trades, and light’s impact on life will transform our buildings.

DOE advisor Monica Hansen looked at the need to create products for lighting requirements instead of combining legacy form factors to reach the desired lighting performance level. Developing mass customizable lighting solutions that can incorporate other value-added functionality to meet the individual needs of a particular space is desirable. Hansen explored a “print on demand” model that can produce the ideal lighting for a space. A lighting photonic integrated circuit (PIC) can create a “lighting system on a chip” as a semiconductor-based, configurable platform that can be designed to provide the required illumination and communication features for a specific space. This forward-looking approach, she said, requires the development of new technology elements with cross-cutting opportunities into other photonics fields and lighting-based applications. Such elements include optical and electrical device integration, a pixelated light source, dynamic optical control features, communication and sensors, a full color tunable spectrum, and packaging innovations. Additive manufacturing, Hansen said, can help integrate the lighting system on a chip into the building space.

Eric Corey Freed of CannonDesign addressed the urgency of climate change and asserted that we can no longer wait to address climate change in the future but instead must figure out how to implement change today – carbon neutral by 2050 is too late. Freed enumerated just some of the issues facing the future and needs and areas for development, including climate change driving up the price on carbon; liability making whole areas uninsurable; the lack of a viable low-carbon solution for concrete; material demand for buildings requiring engineered living materials; and technology to speed construction and reduce costs. He considered if we change what we measure, and how we measure the success of buildings, we can get better outcomes for the occupants. Do we measure success in cost per square foot and payback times, or do we look at metrics such staff retention, occupant comfort, tons of carbon dioxide removed, and kilowatts of energy generated? Buildings should be efficient, healthy, and sustainable, Freed said, adding research into more sustainable building materials is an opportunity area that should be pursued. The way we measure success as an industry must also evolve to look at the right outcomes