Category: LED + SSL

DOE Publishes Results of OLED Stress Testing

The U.S. Department of Energy (DOE) recently released the latest in a series of reports about OLED lighting technology. The new report – Round 2 Update of Stress Testing Results for Organic Light-Emitting Diode Panels and Luminaires – builds on earlier DOE studies of OLED technology by updating information about previously benchmarked OLED products in accelerated stress tests. The results indicate OLED panel performance continues to improve.

The U.S. Department of Energy (DOE) recently released the latest in a series of reports about OLED lighting technology. The new report – Round 2 Update of Stress Testing Results for Organic Light-Emitting Diode Panels and Luminaires – builds on earlier DOE studies of OLED technology by updating information about previously benchmarked OLED products in accelerated stress tests. The results indicate OLED panel performance continues to improve.

DOE stated:

DOE testing shows that the performance of OLED panels continues to improve. The panel shorting and chromaticity maintenance issues that readily occurred in early products are less likely in more-recent ones. However, additional testing is needed to determine whether these failure modes have been completely eliminated, or if their probability for occurrence has been reduced. There are still issues with OLED lighting that must be addressed for it to provide high energy efficiency across products’ lifetime – such as achieving additional gains in luminous efficacy and doing something about the increasing power required for operation as the device ages. The gains in OLED lighting performance and reliability that have been achieved are encouraging and signal the possibility for OLEDs to become significant complements to LEDs in the future. Additional research focusing on new materials with improved performance and higher reliability will help to unlock the commercial potential of this technology in indoor lighting applications.

Click here to check it out.

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LED Reliability Test

In April 2018, the U.S. Department of Energy (DOE) released its final GATEWAY report documenting the performance of LED luminaires in a high-temperature outdoor lighting environment over four years. DOE’s GATEWAY program, which evaluates projects demonstrating LED capability, studied the results of a retrofit of quartz metal halide area lighting along a 7.2-mile stretch in the Yuma, Arizona Border Patrol Area between the U.S. and Mexico. Temperatures in this area can top 100 degrees Fahrenheit at sunset.

Below is a news item I wrote for the October 2018 issue of tED Magazine. Reprinted with permission.

In April 2018, the U.S. Department of Energy (DOE) released its final GATEWAY report documenting the performance of LED luminaires in a high-temperature outdoor lighting environment over four years. DOE’s GATEWAY program, which evaluates projects demonstrating LED capability, studied the results of a retrofit of quartz metal halide area lighting along a 7.2-mile stretch in the Yuma, Arizona Border Patrol Area between the U.S. and Mexico. Temperatures in this area can top 100 degrees Fahrenheit at sunset.

DOE was interested in this project because high-flux lighting, common in street and area lighting and similar applications, can be challenging in an operating environment with high temperatures. DOE wanted to study how this type of environment might affect light output, resulting efficacy, color quality, and service life. The researchers reported a significant decline in light output for the installed first-generation luminaires and color shift for the second-generation luminaires.

In February 2014, three area light poles were retrofitted each with two LED luminaires. Light levels were recorded after 2,500 operating hours (September 2014), 5,000 hours (March 2015), 7,000 hours (September 2015), and 11,000 hours (September 2016). Four second-generation LED luminaires, installed as part of the complete project in September 2016, were tested after 4,000 hours in August 2017.

The new LED lighting reduced energy consumption and maintenance requirements while providing good lighting uniformity—satisfactory results for the Customs and Border Protection. For the first-generation luminaires, however, light levels dramatically declined after 7,000 hours of operation—a 50 percent reduction measured at 11,000 hours. While dirt depreciation was a normal contributing factor, the remainder was due to declining light output.

DOE does not yet know why light output declined so significantly, though an optical issue may have played a part, with Yuma’s high temperatures being the leading suspect. The lesson here is that performance data derived from IES LM-80 may not always be thoroughly accurate predictor of product performance in actual field conditions. And these predictions become even more difficult in extreme conditions such as Yuma’s high-temperature operating environment. DOE called for ongoing improvement of LED system test methods and standards.

The second-generation luminaires installed in September 2016, measured spectral power distribution after 4,000 operating hours showed a variation in color quality (average 152K decrease in correlated color temperature) noticeable on the ground under the lights. The report acknowledged these color differences may not be as noticeable in a more typical area lighting application such as streetlighting, but said it highlights a potential concern when selecting LED luminaires.

Get the report here.

 

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DoE Evaluates High-Efficacy LED Luminaires

In 2017, the U.S. Department of Energy (DoE) evaluated the performance of a selection of LED lighting products with very high published efficacies close to or topping 200 lumens/W. All seven were industrial luminaires, with all but one featuring unshielded light emitters. DoE set out to validate the efficacy claims, characterize commonalities between the products, and identify any performance tradeoffs. Pairs of product samples for each of the seven luminaires were tested for horizontal light level, flicker, and maximum luminance (photometric brightness). Further, 23 knowledgeable observers visually evaluated the products in a mockup.

Below is a news item I wrote for the November issue of tED Magazine. Reprinted with permission.

The seven pairs of high-efficacy LED luminaires installed in a mockup for evaluation. Image courtesy of DoE.

In 2017, the U.S. Department of Energy (DoE) evaluated the performance of a selection of LED lighting products with very high published efficacies close to or topping 200 lumens/W. All seven were industrial luminaires, with all but one featuring unshielded light emitters.

DoE set out to validate the efficacy claims, characterize commonalities between the products, and identify any performance tradeoffs. Pairs of product samples for each of the seven luminaires were tested for horizontal light level, flicker, and maximum luminance (photometric brightness). Further, 23 knowledgeable observers visually evaluated the products in a mockup.

The resulting report was published June 2018.

Efficacy. Light output deviated no more than 9.6 percent and wattage no more than 6.8 percent, while efficacies varied as much as 12 percent from published values. Tested values were often lower than those listed in LED Lighting Facts, which is generally based on best performers in a product family, demonstrating that performance variation in product families is not uncommon.

Light distribution. All luminaires in a mockup high-bay installation emitted light in a reasonably uniform pattern across the task plane, with a maximum-to-minimum light level ratio below 1.7 at a task height of 37 inches off the floor.

Flicker. One of the seven luminaires demonstrated flicker exceeding the Institute of Electrical and Electronics Engineers’ (IEEE) low-risk criteria as defined in Standard PAR1789-2015.

Color quality. Photometric testing showed correlated color temperature (CCT) and color rendering index (CRI) ratings that were in line with manufacturer claims. All seven tested products featured a CCT of 5000K, not surprising as the highest efficacies generally correlate with higher CCTs. Among the tested product types, reducing CCT from 5000K to 3000K produced as much as a 17 percent efficacy reduction.

Photometric brightness. Direct luminance for the exposed LEDs ranged from 154,000 to 478,000 candelas per square meter. One luminaire featured a diffuser that softened luminance to 40,000 cd/m2, a luminance 1.6 times higher than a T5HO fluorescent lamp.

Visual comfort. The most frequent complaint amount the study’s 23 observers was glare, perhaps not surprising given the very high luminances of the products. Only two of the seven products were rated as acceptable for visual comfort and overall quality. These products featured either a diffusing lens or reflector optics that cut off view of the exposed LEDs above a set viewing angle. Both were rated as acceptable for light distribution, shadows, and colors as well as visual comfort. The three lowest-rated products had the most negative complaints about glare.

We can learn several things from this. First, there are LED products that are reaching extraordinary levels of efficacy, though one’s mileage may vary within a product line, especially if there is a choice of CCTs. Next, besides efficacy, other factors such as visual comfort, uniformity, flicker, shadows, and color quality should be given due weight based on the application needs, keeping in mind there may be a tradeoff between efficacy and visual comfort. Ideally, a product under consideration should be evaluated in a mockup before installation.

Get the DoE report here.

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Horticultural Lighting: The Potential of LEDs

In December 2017, the U.S. Department of Energy (DOE) issued a report evaluating the energy-savings potential of LED lighting in horticultural applications. A subsequent May 2018 report by the Lighting Research Center, however, reached different conclusions.

In December 2017, the U.S. Department of Energy (DOE) issued a report evaluating the energy-savings potential of LED lighting in horticultural applications. The DOE concluded that LED lighting offers 24–30 percent energy savings per square foot of grow area. If all horticultural lighting switched to LEDs, total market energy savings would reach 40 percent.

Another research report published by the Lighting Research Center (LRC) in May 2018, however, went further than the DOE report in its analysis and, as a result, produced different conclusions.

Click here to check it out.

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DOE SSL Webinar on October 25: Understanding Technology Tradeoffs in High-Efficacy Luminaires

On October 25 at 2:00 pm EDT, Naomi Miller of Pacific Northwest National Laboratory will examine key findings from a June 2018 Department of Energy study, An Investigation into High-Achieving LED Luminaires, in a webinar that looks at tradeoffs between efficacy, lumen output, light distribution, color temperature, and visual comfort

The 2018 DOE study An Investigation into High-Achieving LED Luminaires evaluated the performance of several LED lighting products with claimed efficacies near or exceeding 200 lm/W.

The purpose of the study was to validate the claimed efficacy, determine the features or characteristics the products had in common, and identify any performance tradeoffs in luminaires reaching this very high efficacy level. All of the products studied were industrial luminaires with CCTs of 5000K, and all but one had exposed LED emitters.

The results of photometric testing of the samples were compared with the manufacturer-claimed values. Additionally, samples were tested for horizontal illuminance, flicker, and maximum luminance, and were also evaluated by 23 knowledgeable observers.

On October 25 at 2:00 pm EDT, Naomi Miller of Pacific Northwest National Laboratory will examine key findings from the study in a webinar that looks at tradeoffs between efficacy, lumen output, light distribution, color temperature, and visual comfort. The presentation will run approximately 40 minutes, with the remaining time allotted for Q&A.

For more information or to register, click here.

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OLED Evaluation

Accounting firm DeJoy, Knauf & Blood LLP (DKB) invited DOE to evaluate a diverse installation of OLED lighting at its Rochester, NY offices comprising about 14,000 sq.ft. One of DKB’s founding partners is a co-founder and CEO of OLEDWorks LLC, the only U.S.-based OLED manufacturer. DOE published the resulting GATEWAY report in 2017, reporting significant energy and quality improvements over the previous fluorescent T8 lighting while gaining insights into OLED’s effectiveness in a real-world setting.

Below is another of my contributions to the May 2018 issue of tED Magazine. Reprinted with permission.

OLED continues to develop as a complementary technology to LED. In 2016, the Department of Energy (DOE) published two reports about the technology: the first, a market assessment, and the second, a GATEWAY report evaluating Acuity Brands’ Trilia OLED lighting system installed in an office application.

More recently, accounting firm DeJoy, Knauf & Blood LLP (DKB) invited DOE to evaluate a diverse installation of OLED lighting at its Rochester, NY offices comprising about 14,000 sq.ft. One of DKB’s founding partners is a co-founder and CEO of OLEDWorks LLC, the only U.S.-based OLED manufacturer. DOE published the resulting GATEWAY report in 2017, reporting significant energy and quality improvements over the previous fluorescent T8 lighting while gaining insights into OLED’s effectiveness in a real-world setting.

The office lighting project features LED lighting with OLED in a supporting role, taking advantage of its strengths and distinctive aesthetic. Acuity Mark LED Slot 2 linear LED luminaires provide general lighting in open offices. Acuity Gotham EVO downlights provide general lighting in private offices, complemented by OLED task lights by OLED Devices. OLED pendants by Acuity, Birot, Designplan, OMLED, and Visa feature prominently in spaces such as break/copy/conference rooms, lounge, and reception desk.

All of the OLED luminaires use OLEDWorks panels and feature dedicated OLED drivers (mounted remotely except for two, which integrate the drivers). When Acuity introduced the Peerless hybrid LED/OLED Olessence luminaire in 2017, which promises an efficacy of 71-81 lumens/W, DKB replaced some of the LED linear products in the open offices. DOE did not test them in its evaluation.

Measured efficacy for the previously installed OLED luminaires ranges from 21 to 58 lumens/W, lower than the LED luminaires (80-90 lumens/W). They are warm in color appearance (around 3000K) and render colors at a measured 79-91 CRI. Nearly all connected to 0-10V dimming controls and dim without flicker. In the nine months of operation, no luminaire failures were reported. Overall, DOE found the OLED lighting to provide comfortable brightness, illumination on vertical surfaces as well as the workplane, and soft, diffuse lighting quality. The total connected load for the LED and OLED lighting is 0.6 W/sq.ft.

This project demonstrates OLED lighting has come a long way over the past five years, though demand continues to be inhibited by its cost premium and low efficacy relative to LED luminaires. Another issue is that as the OLED panels age, they draw more power, which requires compensation in electrical circuit sizing and lighting power calculations. (DOE recommends using an additional power draw of about 15 percent when performing lighting power density calculations.) Next-generation OLED products, however, promise efficacies that are competitive with LED, 90 CRI, and a lifetime of 30,000 to 50,000 hours. This may position OLED well as a complementary technology to LED for general lighting.

Download the DOE GATEWAY report at bit.ly/2ynRiC1.

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Jim Brodrick on LIGHTFAIR 2018

In this republication of a recent Postings, SSL Program Manager Jim Brodrick shares his observations about LIGHTFAIR 2018.

Republication of Postings from the U.S. Department of Energy (DOE) Solid-State Lighting Program

by Jim Brodrick, SSL Program Manager, U.S. Department of Energy

At LIGHTFAIR® International, held a few weeks ago in the Windy City, the U.S. Department of Energy’s (DOE’s) Solid-State Lighting (SSL) team played to standing room only crowds in our award-winning booth, where we offered educational sessions about DOE studies, resources, and tools – such as connected lighting test bed investigations, color rendition research, and Next Generation Lighting Systems installations. But when we weren’t “on stage,” we took the opportunity to walk the show floor, which led to some eye-opening observations.

One of the most notable observations was that manufacturers are clearly focused on product differentiation, and efficiency can be a key factor in that. Many partner with DOE to conduct research that continually raises the efficiency of their products. They’re also focused on exploiting all of the other things that SSL can do. For example, there was definitely an increased emphasis on spectral tuning, compared to what we’ve seen at past LIGHTFAIRS. Many of this year’s booths exhibited LED lighting products that could produce a whole range of colors – even extending to ultraviolet (UV) and infrared – to affect such things as circadian rhythm, productivity, plant growth, and esthetics. Some products we saw could even mimic the progression of daylight throughout the course of a day.

Other levels of control were increasingly apparent as well. In addition to SSL products that could vary the intensity of the light emitted, there were quite a few that featured beam control, with custom secondary optics or dynamic changing beam patterns. One especially interesting technology, which has been incorporated by many luminaire manufacturers, utilizes an LCD flat lens to shape the beam, and looks like it could be a major step for solid-state lighting. The way it works is that the LCD is subjected to a shaped electric field, which orients the LCD crystals in various directions, causing different refractive indexes that allow users to change the luminaire’s beam angle dynamically, depending on the electric field applied.

It was clear from walking the LIGHTFAIR show floor that dim-to-warm is an LED luminaire feature that’s continuing to grow in popularity. And more manufacturers are offering products that dim down to 0.1% output. Zero-10V dimming controls are refusing to die out, with digital addressable lighting interface (DALI) and DMX protocols still taking a back seat because the simplicity and low cost of 0-10V outweigh the drawbacks of voltage-drop issues and confusion between linear and logarithmic dimming curves. Cost and complexity still pose barriers for the other two protocols.

It’s also clear that manufacturers are emphasizing visual comfort through better diffusion and optics, especially in the pedestrian-scale outdoor lighting category, as we saw fewer bare-LED products than we’ve seen at LIGHTFAIR in the past. And many companies were displaying “canless” LED recessed downlights, which are held in place by clips. We also saw a fair number of UVA and UVC LEDs – which, when integrated into luminaires, could increase the value proposition in settings that require disinfection, such as hospital rooms.

On the organic LED (OLED) front, we saw a greater variety of panel offerings – squares, rectangles, circles, and curved panels – and with efficacies of 85 lumens/watt (lm/W), manufacturers are shifting their focus to reducing cost, which remains OLED lighting’s biggest barrier.

It was heartening to see that a number of manufacturers are using IES TM-30-15 metrics – whose development was supported by DOE – to describe the light quality emitted by their products, reflecting the slow but steady progress that, with the help of DOE’s educational efforts, is being made in this area.

And once again, everywhere we looked at LIGHTFAIR, there was connected lighting – which, as the DOE report Energy Savings Forecast of Solid-State Lighting in General Illumination Applications shows, is critical to realizing SSL’s energy-saving potential. But unlike last year, it didn’t feel like connected lighting was the main theme of every LIGHTFAIR booth, because of the increased focus on SSL’s other capabilities and options. Many of those capabilities and options have been enabled, at least in part, by the advances that have been made in efficacy.

But those advances still leave considerable room for improvement. SSL technology on the whole is at a level of maturity that’s comparable to the way cell phones were back in the 1990s. DOE’s role is to conduct early stage research and development that will help SSL evolve to achieve its full potential to revolutionize lighting services and slash energy use.

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DOE Posts LIGHTFAIR Presentations Online

The U.S. Department of Energy once again hosted educational sessions at its LIGHTFAIR booth this year and has now made these presentations available online.

The U.S. Department of Energy once again hosted educational sessions at its LIGHTFAIR booth this year and has now made these presentations available online.

Topics include connected lighting, PoE, flicker, blue light concerns, and color rendering.

Check them out here.

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DOE Announces Up to $15 Million for Early-Stage Solid-State Lighting Research

The U.S. Department of Energy (DOE) recently announced up to $15 million to conduct early-stage, innovative research to drive further breakthroughs in solid-state lighting technology. This funding will accelerate the development of high-quality LED and OLED products.

The U.S. Department of Energy (DOE) recently announced up to $15 million to conduct early-stage, innovative research to drive further breakthroughs in solid-state lighting technology. This funding will accelerate the development of high-quality LED and OLED products.

Topic 1: Core Technology Research for LEDs, OLEDs, and Cross-Cutting Lighting Research
These projects will develop innovative advancements in the underlying science for SSL technology, demonstrating scientific principles, technical application, and application benefits related to physiological impacts of light and light utilization efficiency.

Topic 2: Proof-of-Concept and Prototype Development for LEDs and OLEDs
These projects will pursue early-stage research to contribute to the development of SSL prototypes as well as advanced proof-of-concept SSL materials, devices, and luminaires. Research in this area will focus on high-efficacy LED prototypes, advanced LED lighting, LED power electronics, OLED light engines, OLED prototype lighting platforms, and OLED panel light extraction and utilization.

Topic 3: Advanced Fabrication R&D
These projects will focus on the underlying chemical and physical aspects of SSL fabrication, exploring LED advanced fabrication approaches, OLED substrate and encapsulation fabrication, and OLED panel fabrication.

Topic 4: Innovative Lighting in a Limited Mock Field Application
These projects will assess innovative lighting system solutions in a limited mock field application setting. The technical resources and data sets developed will ultimately help researchers refine or refocus early-stage research and development of SSL-based devices, luminaires, and systems.

In total, the Department will fund approximately 10-15 cost-shared projects from industry, academia, and national laboratories.

Click here to learn more.

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Lighting Facts Revived After DoE Cancellation

D+R International has announced they will continue the Lighting Facts program, recently discontinued by the U.S. Department of Energy.

On April 30, 2018, the U.S. Department of Energy (DoE) announced its LED Lighting Facts program would be discontinued, with the website shutting down June 1. It was earlier reported that this was likely due to budget constraints, while DoE gave the reason that the nearly decade-old program has achieved its objectives.

Very quickly, D+R International, the Lighting Facts private contractor, notified me they are taking over the Lighting Facts program:

LED Lighting Facts will resume acceptance of LED lighting products today, under the direction of D+R International, the implementer of the program since its inception. The simple “truth-in-advertising” labeling program provides consumers with the assurance that the performance of their LED lighting products has been independently verified and that they have an easy in-store and online tool to compare LED lighting products and manufacturers.

D+R will continue the program, which won’t have the DoE affiliation anymore but otherwise should be seamless as a user experience. Current product listings will be free for manufacturers through May, but in June, a subscription pricing model will be introduced. I’ve also learned the program will begin listing lamps again, which were discontinued by DoE in 2016.

Personally, I’m happy to see D+R continue the program, which has arguably benefited the industry.

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